AUTOMATIC  BLOCK  SIGNALS 

AND 

SIGNAL  CIRCUITS 

AMERICAN    PRACTICE    IN    THE    INSTALLATION   AND 

MAINTENANCE     OF     SIGNALS     ELECTRICALLY 

CONTROLLED,      AND      OPERATED     BY 

ELECTRIC   OR   OTHER  POWER 

WITH  DESCRIPTIONS  OF  THE  ACCESSORIES  NOW 
REGARDED  AS  STANDARD 


BY 
RALPH   SCOTT 


FIRST  EDITION 
THIRD 


McGRAW-HILL  BOOK  COMPANY,  INC, 
239  WEST  39TH  STREET.    NEW  YORK 


LONDON:  HILL  PUBLISHING  CO.,  LTD. 

648  BOUVERIE  ST.,  E.  C. 
1908 


COPYRIGHTED,  1908, 

BY 
McGRAW  PUBLISHING  COMPANY 

NEW  YORK 


an  £Hij 

BELOVED  BBOTHEB 
HUGH   EMMOTT    SCOTT 


43863G 


PREFACE. 


THE  evolution  of  a  mechanical  art  results  in  the  simplification 
of  its  apparatus.  The  less  the  number  of  subsidiary  devices 
employed,  and  consequently  the  greater  the  number  of  their 
independent  functions,  the  higher  the  state  of  this  art.  Signal- 
ing accessories,  although  of  rapid  development,  have  not  as  yet 
undergone  the  usage  test  that  is  the  prerequisite  to  standardiza- 
tion and  the  elimination  of  impracticable  differentiated  struc- 
tures. In  surveying  the  heterogeneous  types  of  construction 
employed  in  the  signal  equipment  of  a  representative  rail- 
road system,  the  difficulty  of  selection  and  representation, 
with  respect  to  relative  significance,  becomes  apparent. 

In  a  book  of  this  character,  it  is  extremely  difficult  to  intelligi- 
bly exhibit  continuous  circuits  of  any  great  complication,  owing 
to  the  restricted  space  available  for  illustrations,  insets  not 
having  been  resorted  to.  The  history  of  signaling  is  not  touched 
upon,  as  it  is  irrelevant  to  the  character  of  the  present  work. 
Railroad  terms  have  also  been  omitted,  as  they  are  meaningless 
to  the  average  reader. 

All-electric  interlocking,  a  natural  development  of  the  older 
mechanical  and  electro-pneumatic  interlocking,  is  given  the 
attention  that  its  importance  merits.  Electric  railway  signals 
are  described  as  fully  as  seems  advisable,  since  they  are  in  a 
transitory  state  of  rapid  progress.  Electro-gas  and  three-posi- 
tion signals,  representing  the  highest  development  of  the  art 
in  America,  have  been  treated  not  only  from  an  electrical  stand- 
point, but  also  from  a  structural  point  of  view. 

This  book  is  intended  for  the  signal  and  railway  engineer,  the 
electrician,  and  the  layman;  and  it  is  modestly  hoped  that  it 
will  appeal  to  all  in  any  way  concerned  with  signaling. 

iii 


iv  PREFACE 

The  old  argument  of  normal  danger  vs.  normal  clear  is  not 
taken  up ;  nevertheless,  data  on  both  these  systems  of  indication 
is  given  throughout  the  book,  the  reader  being  left  to  his  own 
conclusions  as  to  their  relative  merits. 

The  writer  wishes  to  acknowledge  several  courtesies  received 
from  the  signal  companies  whose  products  have  of  necessity 
been  described,  and  also  to  Messrs.  H.  S.  Balliet,  J.  C.  Jones, 
B.  H.  Mann,  M.  E.  Smith,  W.  W.  Slater,  and  A.  J.  Wilson. 

Criticisms  are  respectfully  invited. 

R.  S. 

WlLKESBARRE,   PA. 


CONTENTS. 


CHAPTER.  PAGE. 

I.     PRELIMINARY  CONSIDERATIONS 1 

II.     SIMPLE  CIRCUITS 15 

III.  NORMAL  DANGER  CIRCUITS 30 

IV.  NORMAL  CLEAR  CIRCUITS 50 

V.     SEMI-AUTOMATIC  CIRCUITS 68 

VI.     BATTERIES 84 

VII.     THB  TRACK  CIRCUIT 95 

VIII.     CONTROLLED  MANUAL  SYSTEMS 105 

IX.     MOTORS,  RELAYS,  ETC 119 

X.     HALL  APPARATUS 131 

XI.     UNION  APPARATUS 147 

XII.     ELECTRO-PNEUMATIC  AND  ELECTRO-GAS  SIGNALS 160 

XIII.  ELECTRIC  LOCKING 171 

XIV.  ALL-ELECTRIC  INTERLOCKING 179 

XV.    THRBE-POSITION  SIGNALS 201 

XVI.     ELECTRIC  RAILWAY  SIGNALS 215 

XVII.  MAINTENANCE..                                                                                     ..226 


AUTOMATIC  BLOCK  SIGNALS. 


CHAPTER  I. 
PRELIMINARY   CONSIDERATIONS. 

A  block  is  a  length  of  railroad  track  of  defined  limits,  the  use 
of  which  by  trains  is  under  the  control  of  one  or  more  block 
signals. 

A  block  signal  is  a  fixed  arrangement  controlling  the  use  of  a 
block. 

An  automatic  block  signal  is  one  automatically  operated  by 
electrical  or  other  energy,  this  agency  being  controlled  by  the 
passage  of  trams  along  the  track,  or  by  conditions  which  interfere 
with  such  movement. 

A  block  system  is  a  series  of  consecutive  blocks  controlled  by 
block  signals. 

A  home  signal  shows  the  condition  of  the  block  directly  in 
front  of  a  moving  train;  and  a  distant  signal  the  condition  of  the 
second  block  in  front,  or  the  block  in  the  rear  of  the  home  block. 

An  advance  signal  shows  the  condition  of  a  block  in  conjunc- 
tion with  the  home  signal  of  that  block.  It  is  placed  in  advance 
of  the  home  signal. 

In  Fig.  1  two  signals,  having  home  and  distant  semaphores, 
blades,  or  boards,  are  shown,  with  the  track  protected  by  each; 
train  movement  being  in  the  direction  of  the  arrows.  The  en- 
tire home  block,  consisting  of  two  sections  of  the  first  signal,  is 
represented;  and  one  section  of  the  home  block  of  signal  2, 
which  latter  is  also  the  first  section  of  the  distant  block  of 
signal  1. 

A  block  is  usually  made  about  one  mile  long,  although  a  large 
amount  of  traffic,  the  presence  of  an  interlocking  plant,  numer- 
ous switches,  or  the  necessity  of  slow-speed  movements  may 

l 


t  '  2's  f-     «  *    *     *     i  TTmV"*'i>r  A  mrsv 


AUTOMATIC  BLOCK  SIGNALS 

require  less  length.  On  the  other  hand,  blocks  in  a  sparsely 
settled  district,  with  thin  traffic,  can  be  of  greater  length.  These 
blocks  are  protected  in  automatic  visual  systems  by  a  disk, 
semaphore,  or  revolving  member  by  day,  and  by  colored  lights 
at  night;  these  giving  warning  of  the  presence  of  a  train,  broken 
rail,  open  switch,  car  outside  the  clearance  point  at  sidings,  an 
open  drawbridge,  hand  car  on  the  track,  or  defect  in  the  appa- 
ratus. 

There  are  several  wrays  of  indicating  a  danger,  caution,  or 
clear  condition,  among  which  are:  (1)  color  systems;  (2)  position 
systems;  (3)  motion  systems.  A  type  of  the  first  is  a  colored 
disk  moving  before  a  white  surface,  either  the  former  or  the  latter 
being  visible;  of  the  second,  a  blade  or  semaphore  which  is  held 
at  various  angles  to  the  track;  when  horizontal,  "  danger  "  or 


rails 


\<— cut  section— b — cut  section-^ 

Ho.  i.  Wo.z. 

\t home  iloch  [of  signal  i] — >| 

FIG.  1 

"  stop  "  being  indicated,  and  when  nearly  vertical,  "  proceed  " 
or  "  clear."  Semaphores  may  be  colored  also,  and  thus  become 
of  the  first  type.  The  third  or  motion  signal  utilizes  a  revolving 
member,  whose  motion  indicates  that  an  approaching  train  may 
continue  to  move,  and  when  stationary  that  the  engine  must 
come  to  a  stop.  At  night  a  light  is  flashed  intermittently  by 
this  member.  Such  systems,  and  also  illuminated  semaphores, 
have  been  abandoned,  and  therefore  will  not  be  described. 

Usually,  signals  are  numbered  in  such  manner  that  these 
numerals  will  indicate  the  number  of  miles  and  tenths  of  a  mile 
that  the  signal  is  distant  from  the  chosen  terminal.  Thus  on 
the  Lehigh  Valley,  signal  No.  1773  is  177.3  miles  from  New  York 
City.  On  this  road,  odd  numbers  designate  west  bound  signals 
and  the  even  numbers  the  east  bound  signals.  Thus  it  is  evident 
that  1773  is  the  west  bound  signal  177.3  miles  from  New  York 


PRELIMINARY  CONSIDERATIONS 


3 


City  (the  nearest  odd  number  to  the  actual  tenth  of  a  mile  being 
chosen). 
Fig.  2  shows  four  separate  main  tracks  intersecting  at  right 


wetbound 


fe 


easoun 


FIG.  2 

angles,  with  their  respective  signals.    If  these  are  automatic, 

track  relays,  properly  interconnected,  can  be  readily  arranged 

to  give  the  protection  de- 

sired.   If  they   are  semi- 

automatic,   electric    inter- 

locking will  be  introduced        red- 

to    prevent    conflicting  of 

routes.    Thus,  when  signal 

3  is  at  clear,  to  allow  a 

south  bound  train  to  pass, 

1,  2,  and  4  must  be  locked 

in  the  normal  or  stop  posi- 

tion when  electric  locking 

or  interlocking  is  used,  and 

prevented  from  moving  to 

clear  if  the  ordinary  auto- 

matic  system  is  employed. 

A  standard  sixty-degree  home  and  distant  semaphore  arrange- 
ment is  shown  in  Fig.  3.    Until  either  blade  has  reached  a  po- 


Tiome  semaphore 

I 

white  or  Hack 
yettow 


distant  semaphore 


FlG  3 


4  AUTOMATIC  BLOCK  SIGNALS 

sition  approximating  thirty  degrees  from  the  vertical  it  will 
indicate  the  same  as  though  at  the  full  horizontal  position.  This 
is  effected  by  using  several  spectacles,  each  held  in  place  by  in- 
dependent bezel  rings,  or  by  so-called  continuous  light  spectacles. 
Semaphores  vary  in  length  from  four  to  five  feet,  about  four  and 
one-half  being  regarded  as  standard. 


FIG.  4 


FIG.  5 


A  self-contained  standard  home  and  distant,  three-spectacle, 
semaphore  signal  (electro-gas  or  motor ),  is  shown  in  Fig.  4,  the 
motor,  mechanism  and  battery  housings  being  at  the  base. 
This  represents  the  highest  development  in  external  design 
that  such  signals  have  reached,  unless  exception  be  made  of 
the  top  post  arrangement. 

A  three-spectacle,  automatic,  double-route,  home  and  distant 
semaphore  signal  is  illustrated  in  Fig.  5.  The  post,  B,  consists 


PRELIMINARY  CONSIDERATIONS 


of  two  lengths  of  channel  iron  strengthened  by  a  lattice  structure, 
the  base  being  bolted  to,  or  incorporated  with,  a  foundation  of 
concrete,  A.  The  top  consists  of  a  platform,  G,  and  railing,  E, 
semaphores,  F,  being  pivoted  to  short  posts  and  operated  by 
motors  and  accessories  housed  in  the  waterproof  base  boxes, 
C-D.  This  arrangement  represents  the  latest  order  of  con- 
struction for  the  protection  of  two  tracks  having  trains  running 
hi  the  same  direction. 

In  Fig.  6  A  is  a  short  mast  distant  semaphore  signal  with  an 
automatic  mechanism  housing  at  the  base;  B  is  a  high  home 
signal;  C  a  short  mast  two-arm  or  double-route,  D  a  high  mast 
two-route,  and  E  a  three-arm  or  triple-route  arrangement.  The 


T  - 

?-    - 

0 

» 

—  s 

mm 

-M 

S 

( 

i 

0 

V 

A 

5 

k          i 

Z7 

\ 

FIG.  6 

standard  heights  of  each  are  also  given,  and  although  this  latter 
may  vary  somewhat,  it  represents  the  usual  practice. 

Bridge  signals,  which  are  of  more  substantial  design  than 
mast  signals,  are  shown  hi  Fig.  7.  The  letters  designate  types 
similar  to  those  in  the  preceding  figure.  The  tracks  pass  be- 
neath the  bridge  at  G.  Most  lines  having  four  main  tracks  or 
over  use  this  disposition  of  semaphores. 

Fig.  8  shows  two  forms  of  motor-operated  high  signals,  A 
being  a  single  arm,  and  B  a  two-route  arrangement.  The  cir- 
cuit breakers,  H,  are  operated  by  the  rods,  Or,  connected  to  the 
semaphore  castings.  The  cast  iron  box,  A,  contains  the  motor 
and  gearing  constituting  the  signal  movement  (see  Fig.  119), 
and  part  of  the  sheave,  B,  which  carries  the  chains,  C,  projecting 


6 


AUTOMATIC  BLOCK  SIGNALS 


from  below.  The  blades  are  connected  to  the  counter-weighted 
levers,  E,  resilient  members,  D,  being  introduced  to  prevent  in- 
jury to  the  parts  when  they  fall,  or  should  the  motor  wind  up 
too  high.  Reversal  of  the  motor  on  B  is  effected  by  a  ground 
selector,  described  in  Chapter  XIV. 

The  electric-motor  semaphore  signal  has  several  advantages, 
among  which  may  be  mentioned:  (1)  localization,  it  being  self- 
contained,  and  therefore  independent  of  all  other  signals;  (2) 
comparatively  large  reserve  power;  (3)  an  isolated  plant  is  not 
required  for  its  operation;  (4)  economy  of  installation  and  opera- 
tion; (5)  working  and  control  functions  are  unified;  (6)  external 
simplicity  of  design. 


xx>too< 


B 


KX>*<X>f<X>«Q<X 


FIG.  7 


The  motor  and  control  mechanism  is  somewhat  complicated, 
and  numerous  factors  of  failure  have  been  necessarily  intro- 
duced. A  clumsy  structure  is  used  to  transform  the  high-speed 
rotary  armature  movement  into  a  slow,  direct  reciprocating 
motion,  while  the  motor  itself  is  not  a  perfectly  reliable  device 
under  the  restrictions  that  must  be  imposed  upon  it.  Frost  may 
accumulate  upon  the  commutator,  the  lubricant  may  gum,  or  the 
mica  cause  an  open  circuit,  thus  resulting  in  inoperation.  The 
clutch  or  slot  magnet  armatures  may  also  freeze  in  the  clear 
position,  as  they  are  not  acted  upon  by  a  powerful  force. 

The  generic  purpose  of  the  electric  circuits  applied  to  devices 


PRELIMINARY  CONSIDERATIONS          1 

whose  electrical  operation  establishes  the  right  of  train  move- 
ment, is  to  prevent  conducting  continuity  when  a  conflicting  or 
non-clear  condition  exists.  Thus  imagine  a  home-signal  recep- 
tive device  whose  energization  cannot  occur  until  twenty-four 
independent  contacts  have  been  closed,  each  having  a  function 


D 

£• 


ff 


n 


FIG.  8 


which  determines  the  right  to  proceed;  then  the  opening  of  any 
one  or  more  of  these  prevents  the  flow  of  current  which  is 
obviously  the  concomitant  of  a  clear  condition.  It  is  the 
comprehension  of  this  principle  which  will  render  evident  the 
application  of  signal  circuits  and  their  close  approach  to  being 
an  ideal  selective  intermediary. 


8  AUTOMATIC  BLOCK  SIGNALS 

Commercial  signal  circuits  may  be  divided  into  two  parts, 
which  are  more  or  less  generic  according  to  the  system 
employed.  These  are  respectively  control  circuits  and  working 
circuits. 

Usually  a  control  circuit  has  a  relatively  low  impressed  vol- 
tage, and  the  circuit  wires  are  not  of  great  length.  The  most 
common  type  of  control  circuit  is  that  constituting  what  is  ordi- 
narily termed  the  "track  circuit/'  which  includes  the  rails  of  the 
section  to  which  it  is  applied,  with  the  requisite  track  battery, 
relay,  and  interconnecting  wires.  The  primary  purpose  of  the 
control  circuit  is  to  close  and  open  another  circuit,  the  latter 
delivering  considerable  energy  and  actuating  the  devices 
included  in  the  direct  operation  of  the  signal  banner  or 
semaphore. 

This  latter  constitutes  the  working  circuit.  The  main  bat- 
tery, which  is  in  this  circuit,  cannot  be  short-circuited,  owing  to 


FIG.  9 

the  loss  of  energy  which  would  result,  the  deleterious  effect  upon 
the  cells,  and  the  excessive  sparking  at  the  shunt  contact, 
which  latter  would  necessitate  the  use  of  unusually  heavy  or 
special  circuit  breakers.  With  a  resistance  in  series,  such  as 
the  line  wire,  motor,  slot  magnets,  or  other  accessories,  these 
precautions  do  not  apply. 

Considering  the  arrangement  in  Fig.  9,  with  a  normally  clear 
signal,  S,  whose  current  is  obtained  from  a  battery  in  shunt  with 
the  rails  of  the  insulated  track  section,  A-B,  it  is  evident  that 
as  soon  as  a  car,  train,  or  locomotive  passes  along  this  section  in 
the  direction  of  the  arrow,  the  resulting  short-circuiting  of  the 
battery  will  deprive  the  signal  of  current,  and  thus  throw  the 
semaphore  to  the  danger  position.  A  train  which  is  on  any 
other  section  of  the  rails  will  not  affect  this  signal,  which  there- 
fore indicates  only  the  condition  of  the  section  it  immediately 
precedes.  Such  a  circuit,  while  readily  comprehended,  is  not 
commercially  practicable  for  the  following  reasons: 


PRELIMINARY  CONSIDERATIONS  9 

(1)  Too  great  a  length  of  line  wire  is  required. 

(2)  Unnecessary  waste  of  energy,  due  to  the  short-circuiting 
of  the  battery. 

(3)  Adequate  protection  is  not  afforded  (for  reasons  that  will 
be  clearer  later). 

(4)  Too  great  a  current  loss  will  occur,  due  to  the  high  differ- 
ence of  potential  between  the  rails. 

The  principle  of  introducing  series  switch-contacts  to  throw  a 
signal  at  danger  when  track  switches  in  its  block  are  opened  into 
the  home  circuit  of  a  signal  is  set  forth  in  Fig.  10.  In  the  block 
of  S  are  three  switches,  C,  E,  and  G,  having  three  switch  in- 
struments, A,  D,  and  K.  Battery  B  energizes  the  operating 
mechanism  of  the  home  semaphore,  H,  through  the  successive 
relay  points  and  the  single  pole  contacts  at  A,  D,  and  F.  There- 
fore, should  either  of  these  switches  be  thrown  open,  the  signal 


FIG.  10 

circuit  will  be  broken  and  the  signal  held  at  danger,  regardless 
of  the  condition  of  the  relay  contacts. 

In  general,  it  is  better  to  place  the  dependence  of  a  safety 
condition  or  a  danger  indication  upon  the  opening  of  a  circuit 
rather  than  its  closing.  In  the  low-voltage  circuits  used  in 
signaling,  there  is  greater  certainty  in  opening  than  in  closing  a 
contact.  This  is  because  a  poor  connection  (or  particles  of  dirt 
preventing  the  intimate  metallic  contact  which  is  the  prerequisite 
of  a  closed  circuit)  may  introduce  a  sufficient  resistance  or  air- 
gap  to  oppose  the  desired  flow  of  current.  As  an  example,  the 
closed-circuit  and  open-circuit  types  of  switch  instruments  may 
be  cited.  In  the  former,  with  an  open  switch,  the  track  must 
be  short-circuited;  in  the  latter,  the  signal  circuit  must  be  opened 
to  hold  the  signal  at  danger.  The  latter  is  obviously  the  most 
reliable,  as  a  poor  contact  will  merely  mean  a  false  danger 


10  AUTOMATIC  BLOCK  SIGNALS 

condition,   while  in  the  former,  it  will   set  up  a  false  clear 
signal. 

Nearly  all  existing  types  of  automatic  signals  may  be  used  in 
a  semi-automatic  sense;  for  example,  placed  at  an  outlying 
switch  or  interlocking  scheme,  and  controlled  by  a  line  or  track 
circuit  from  the  nearest  tower.  Such  a  provision  eliminates  the 
use  of  cumbersome  and  costly  mechanical  interconnection,  and 
involves  no  appreciable  labor  on  the  part  of  the  operator  in 
clearing  or  releasing.  When  the  track  circuit  is  used,  the  oper- 
ation of  this  signal  is  taken  from  the  immediate  control  of  the 
tower  operator,  although  the  conditions  required  to  be  set  up 
by  train  movement  may  class  the  signal  as  not  purely  auto- 
matic. The  extension  of  these  principles  will  be  considered  in 
Chapter  V. 

The  conditions  that  may  set  up  a  false  or  dangerous  condi- 
tion in  a  signal  system  are  manifold ;  but  their  actual  occurrences 
few.  The  failures  at  danger  can  only  wrongly  delay  a  train; 
but  failures  at  clear,  by  giving  the  engineer  a  proceed  indication 
when  such  may  not  be  safe,  are  the  only  ones  that  can  really  be 
termed  dangerous.  Such  failures  have  in  practice  occurred  on 
an  average  of  one  in  a  million  movements.  On  a  normal  clear 
system,  an  average  of  one  in  about  six  hundred  thousand  has 
often  been  reported.  Many  such  failures  occur  from  inability 
of  the  moving  system  to  move  from  its  normal  position.  It  is 
not,  primarily,  the  external  parts  which  are  sensitive  to  such 
checks  to  movement,  as  they  are  thrown  by  a  powerful  force, 
and  with  sufficient  inertia  to  remove  a  retardation ;  but  the  light 
control  parts,  whose  motion  is  due  to  the  expenditure  of  energy 
measured  in  thousandths  of  a  watt. 

Among  the  causes  of  false  clear  conditions  are,  fusing  of  con- 
trol contacts,  improperly  counterweighted  banner  or  semaphore, 
breaking  of  the  color  spectacles,  rusting  of  sliding  parts,  foreign 
currents,  residual  magnetism  in  relays,  imperfect  contacts,  dust 
or  insects  in  relay  boxes,  crossing  or  grounding  of  wires,  inter- 
connection of  wires  with  common,  poor  armature  pivots,  failure 
of  clutches  or  locks  to  return,  breaking  of  mechanical  connec- 
tions, and  poorly  insulated  circuit  wires. 

The  use  of  white  as  a  clear  indication  is  meeting  with  dis- 
favor. This  is  due  to  the  liability  of  a  spectacle's  breaking,  or 
the  chipping  off  of  its  color  film.  The  adoption  of  green  or  red 


PRELIMINARY  CONSIDERATIONS  11 

for  clear  has  many  advantages,  among  which  are  the  normal 
danger  indication  of  a  white  light,  except  when  a  color  spectacle 
is  actually  and  properly  before  it,  and  the  restricted  conditions 
under  which  safety  indications  are  given. 

Failures  at  danger  may  be  caused  by  a  broken  rail,  bond  wires 
rusted  off  or  broken,  rusty  channel  pin,  high-current  leakage 
between  the  tracks,  broken  wires  in  the  relay,  polarity  reverser, 
track  battery  or  signal  circuit,  exhausted  track  or  main  batter- 
ies, poor  connections,  unsoldered  joints,  broken  battery  jar, 
useless  or  poor  connection  in  switch  boxes  or  controllers,  blowing 
of  the  protective  fuses,  failure  of  an  arrester,  broken  line  wires, 
short-circuiting  of  an  individual  or  series  of  batteries,  open  cir- 
cuit at  motor  commutator,  failure  of  electric  slots  or  locks, 
poor  insulation,  short-circuits  in  relays,  and  the  depredations  of 
mischievous  persons. 

As  far  as  visual  indication  is  concerned,  the  normal  danger 
position  is  undoubtedly  the  best,  and  has  been  so  recognized 
since  the  inception  of  mechanically  operated  semaphores;  while 
argumentative  opinion,  from  a  purely  electrical  standpoint, 
also  favors  such  a  disposition.  Formerly,  standard  normal 
clear  circuits  were  more  economical  in  initial  installation,  but 
this  consideration  no  longer  obtains. 

Various  signal  engineers  and  others  have  from  time  to  time 
regarded  a  certain  modification  or  departure  as  ideal.  Such 
arrangements,  when  actually  applied,  have  frequently  an  ephe- 
meral existence.  In  no  specific  instance  has  such  unproductive 
effort  been  expended  as  in  rail  bonding.  Railroad  accessories 
undergo  hard  usage,  and  are  subjected  to  extremes  of  weather, 
so  that  a  scheme  which  seems  temporarily  of  a  revolutionary 
character  is  found  hopeless  after  a  few  years  of  service.  The 
greater  part  of  the  accessories  introduced  since  automatic  sig- 
naling began  have  been  abandoned  for  this  reason,  so  that 
standardization  appears  distant  when  viewed  from  the  present. 

Numerous  attempts  have  been  made  to  introduce  protective 
arrangements  supplementary  to  a  visual  system,  in  which  the 
control  of  a  train  is  taken  temporarily  from  the  engineman 
in  case  a  danger  signal  is  ignored  or  unapprehended.  Fig.  11 
shows  an  impracticable,  though  a  generic  form  of  such  an  ac- 
cessory. When  the  home  semaphore  is  in  the  danger  position, 
it  raises  a  finger  or  projection  which  engages  with  a  pivoted 


12 


AUTOMATIC  BLOCK  SIGNALS 


lever  secured  to  one  of  the  trucks  of  a  train.  This  lever,  B,  is 
fastened  to  a  valve,  A,  which  is  connected  to  the  train  pipe,  T, 
of  the  air  brake  equipment  by  a  flexible  tube,  C,  the  travel  of 
this  lever  being  limited  by  the  quadrant  D.  Obvious  reasons 
can  be  advanced  against  the  application  of  such  a  device.  We 
will  take  up  in  Chapter  XVI  a  development  of  this  principle, 
which  has  the  merit  of  being  in  use. 

The  normal  danger  system  admits  of  the  employment  of  nor- 
mally open-track  circuits.  This  condition  allows  the  use  of 
open-circuit  batteries  (gravity  cells  cannot  be  employed)  with 
consequent  economy  of  operation.  Instead  of  the  customary 


FIG.  11 

two  weeks'  intervals  between  patching  and  renewing,  it  is  pos- 
sible to  run  six  months.  The  circuits  are  closed  in  the  preced- 
ing two  blocks  by  the  approaching  train,  and  should  anything 
be  wrong  in  the  block,  the  track  relays  will  receive  no  energiza- 
tion. The  continual  heavy  demand  upon  track  batteries  by 
the  low-resistance  track  relays  under  a  clear  track  condition  has 
been  heretofore  one  of  the  greatest  disadvantages  of  signal 
installation. 

In  Fig.  12  a  diagrammatic  representation  of  relays  and  con- 
tacts, such  as  is  used  throughout  this  book,  is  given.  A  has 
one  front  (upper)  and  one  back  (lower)  contact,  each  being 
a  single-pole  break,  and  so  disposed  that  both  cannot  be  in 


PRELIMINARY  CONSIDERATIONS  13 

simultaneous  contact  with  the  armature.  B  is  a  single  front 
contact,  and  is  more  frequently  applied  than  any  other  combina- 
tion. C  has  two  front  contacts,  with  independent  armatures; 
D  two  front  and  one  back;  E  three  front  with  common  arma- 
ture; F  two  front  and  two  back;  G  three  front  with  independent 
armatures;  and  H  four  front  and  four  back,  each  having  a 
double  simultaneous  break.  In  reality,  these  connections  are 
usually  effected  by  a  single  armature  on  each  relay,  but  a  more 
definite  conception  is  afforded  by  representing  as  shown. 

The  application  of  automatic  signals,  by  giving  to  trainmen 
the  right  to  shift  their  trains  at  all  reasonable  times,  renders  im- 
perative a  positive  knowledge  of  the  condition  of  the  track  to 
which  they  are  to  proceed.  Should  a  train  be  approaching  this 


block  or  is  already  within  it,  there  must  be  some  means  of  warn- 
ing the  trainmen  not  to  open  the  switch.  Should  such  a  switch 
be  opened,  the  main  line  signal  must  be  held  at  danger,  and  in- 
formation be  conveyed  to  the  trainmen  that  it  has,  and  that 
the  opening  of  the  switch  was  the  cause  of  such  movement. 
This  is  now  accomplished  by  means  of  a  polarized  indicator,  as 
the  neutral  type  cannot  be  thus  applied;  for,  if  a  train  enters 
the  main  block  in  question  at  the  moment  the  switch  has  been 
thrown,  the  trainman  will  necessarily  assume  that  he  has  been 
the  cause  of  such  indicator's  movement,  and  unconsciously  pro- 
ceed to  the  main  line  without  expectation  of  danger.  Thereby 
delay  would  result  to  the  train  passing  the  main  signal,  if  the 
latter's  indication  were  understood  by  the  engineman,  but 
should  the  latter  fail  to  note  the  condition  of  the  block,  a  colli- 
sion might  result. 


14  AUTOMATIC  BLOCK  SIGNALS 

Primary  cells  are  employed  almost  exclusively  for  the  opera- 
tion of  automatic  signals,  because  of  their  peculiar  adaptability 
to  the  requirements  of  these  devices.  Although  not  nearly  so 
economical  as  other  methods  of  setting  up  currents  of  electric- 
ity, yet,  when  a  small  amount  of  energy  is  to  be  delivered  con- 
tinuously, or  for  long  periods  of  time  with  extreme  reliability, 
the  question  becomes  not  economy,  but  constancy  of  operation. 

Thermoelectric  devices,  in  which  currents  have  been  set  up 
directly  from  heat,  have  been  tried,  but  as  yet  have  been  found 
wanting,  owing  to  their  multiplicity  of  parts  and  the  necessity 
of  maintaining  a  flame  continuously.  Improvements  along  this 
line  are  anticipated,  but  may  be  hopelessly  remote. 


CHAPTER  II. 
SIMPLE  CIRCUITS. 

SIGNAL  circuits  admit  of  innumerable  variations;  and  nearly 
every  installation  requires  a  special  scheme  of  interconnection. 
There  are,  however,  certain  generic  features  adhered  to  which 
obtain  in  most  cases.  It  is  their  differentiation  which  produces 
the  seeming  complexity  when  viewed  as  a  whole.  A  number  of 
simple  circuits  and  their  modifications  will  now  be  taken  up. 

The  circuit  diagram  for  an  old  style  of  disk  signal  is  shown  in 
Fig.  13.  The  main  battery  11  is  connected  to  the  track,  15, 


train 

FIG.  13 

and  through  the  latter  to  two  relays  at  signals,  14  and  12,  in 
series  with  the  line  wires,  1  and  2.  The  signal  connections  are 
similar,  and  consist  of  a  clearing  electromagnet,  6,  and  a  stop 
magnet,  5,  whch  are  connected  respectively  to  the  connects,  9 
and  10,  of  the  armature  of  3,  the  latter  being  pivoted  at  8,  and 
weighted  at  13.  With  a  train  in  the  block,  11  is  short-circuited, 
hence  the  relays  are  deenergized,  their  armatures  touching  the 
upper  contacts,  and  closing  the  local  circuit  of  4  through  6,  as 
shown.  Thus,  when  the  block  is  occupied,  6  is  energized; 
when  not,  5  is  energized.  A  disadvantage  of  this  method  of 
connection  is  the  great  waste  of  energy  when  11  is  short-cir- 

15 


16 


AUTOMATIC  BLOCK  SIGNALS 


cuited,  and  the  dangerous  effects  of  a  connection  between  line 
wires  1  and  2. 

It  frequently  becomes  advisable  to  control  a  distant  signal 
from  a  manually  or  automatically  operated  home  signal  through 
the  interposition  of  a  circuit  controller.  Such  an  arrangement 
of  circuits  is  given  in  Fig.  14,  and  provides  for  a  power-operated 


5U 


FIG.  14 

distant  signal.  The  latter,  shown  at  D,  is  governed  by  the  cir- 
cuit controller,  G.  When  the  latter  is  closed  (which  will  occur 
when  the  home  signal,  B,  is  thrown  to  the  clear  position  by  the 
operator  at  the  signal  tower,  T)  the  line  battery,  A,  sends  current 
through  the  relay,  (7,  at  the  other  end  of  the  line,  which  raises  the 
armature,  F,  of  the  latter,  closing  the  motor  circuit  of  the  local 
battery,  E,  and  thereby  throws  D  to  the  clear  position. 


o 


D 


FIG.  15 

If  the  above  arrangement  does  not  include  sufficient  precau- 
tionary measures,  other  functions  are  included  which  will  pre- 
vent, in  various  ways,  the  conflicting  of  routes,  false  indications, 
and  delay  in  train  movement.  It  is  the  proper  recognition  of 
these  factors,  and  their  successful  elimination,  which  produces 
the  complexity  often  met  with  in  signal  circuits.  In  Fig.  15, 


SIMPLE  CIRCUITS 


17 


a  switch,  K,  is  introduced  in  the  simple-control  circuit  given 
above,  which  requires  operation  by  the  tower  attendant  before 
the  distant  signal  will  assume  the  clear  position.  This  condi- 
tion is  effected  by  including  it  in  series  with  the  line  battery  and 
relay  governing  the  distant  signal's  motor  circuit. 
In  Fig.  16  is  shown  a  circuit  arrangement  which  employs  a 


" 


FIG.  16 


vibrating  bell,  (7,  to  communicate  the  desired  announcement  of 
the  motion  of  a  distant  signal  blade,  D,  to  the  tower  operator. 
Motion  of  the  semaphore  produces  a  movement  of  the  contact 
arm  of  the  special  controller,  A,  and  consequently  closes  the 
circuit  of  the  battery,  B,  in  which  C  is  included.  This  controller 


PI 

if       -1 

uZ  —  m 

^£ 
1                 i    i 

1        0 

f\ 

"U 

r 

FIG.  17 

is  so  arranged  that  when  the  blade  is  in  either  the  extreme  cau- 
tion or  clear  position  the  circuit  is  opened.  While  the  blade  is 
moving,  on  the  other  hand,  the  circuit  is  closed.  C  may  be  a 
combination  bell  and  indicator,  or  it  may  include  a  setting  device. 
A  visual  indication  of  the  clear  or  caution  position  of  a  distant 
signal  requires  the  use  of  an  indicator,  as  shown  in  Fig.  17,  at  E. 


18 


AUTOMATIC  BLOCK  SIGNALS 


When  C  is  closed  by  the  motion  of  the  semaphore  of  D,  the 
battery  circuit  is  completed  and  the  armature  of  E  will  be  raised, 
in  the  type  of  indicator  illustrated.  Another  type  is  used,  how- 
ever, which  will  indicate  clear  when  its  armature  falls,  requiring 
the  use  of  a  controller  whose  make  and  break  is  in  the  opposite 
sense  to  that  shown. 


FIG.  18 

In  Fig.  18  we  have  a  semi-automatic  arrangement  of  circuits 
in  which  the  circuit  controller,  D,  is  operated  by  the  representa- 
tive lever,  A,  of  an  interlocking  machine.  This  lever  controls 
by  its  mechanical  movement  a  certain  function,  the  electrical 
adjuncts  being  for  another  and  distinct  purpose,  but  of  a  con- 
comitant nature,  in  the  scheme  of  protection.  When  A  is 
thrown  in  the  direction  of  the  arrow,  the  circuit  of  the  line  bat- 
tery, B,  is  closed,  thus  energizing  the  distant  relay,  E,  which, 
through  its  armature,  H,  sends  a  clearing  current  from  the  local 
battery,  G,  through  the  distant  signal,  F. 


kL* 


FIG.  19 


In  Fig.  19  the  same  principle  is  contemplated,  but  in  addition 
a  circuit  controller,  M,  is  employed,  which  thus  prevents  the  dis- 
tant signal  from  being  cleared  until  the  function  the  controller 
protects  has  been  properly  manipulated.  This  function,  as  will 


SIMPLE  CIRCUITS 


19 


be  shown  throughout  this  book,  may  have  any  desired  applica- 
tion or  complexity. 

In  Fig.  20  we  have  another  semi-automatic  scheme  of  connec- 
tion for  a  distant  signal;  the  bonded  track  circuit  being  used 
instead  of  line  wires.  The  track  battery,  T,  maintains  a  differ- 
ence of  potential  across  the  section,  S,  and  normally,  by  energiz- 


n: 


FIG.  20 

ing  the  track  relay,  R,  causes  a  current  to  pass  from  the  local 
main  battery,  B,  to  the  distant  signal,  Z),  through  the  armature, 
C.  When  H  is  cleared,  the  controller,  A,  is  closed,  and  the 
reverse  condition  of  affairs  to  that  given  in  the  figure  obtains. 
Such  an  arrangement  is  more  desirable,  and  less  complicated 
than  a  line-wire  system. 


FIG.  21 

The  above  distant  signal  cannot  be  controlled  otherwise  than 
through  the  movement  of  the  home  board.  It  sometimes  is  advis- 
able to  give  the  signalman  authority  to  throw  the  distant  board 
to  caution  without  altering  the  clear  position  of  the  home  signal. 
This  is  effected  as  shown  in  Fig.  21.  When  H  is  cleared,  B  will 
be  closed  as  before.  In  addition,  the  hand  switch,  A,  must  be 
closed,  or  the  track  relay,  E,  cannot  be  energized  due  to  the 


20 


AUTOMATIC  BLOCK  SIGNALS 


position  of  the  armature  of  C,  and  its  connection  with  track 
battery,  D.  Thus,  when  both  A  and  B  are  closed,  the  distant 
signal  can  be  cleared.  The  armature  of  C,  by  short-circuiting 
the  track,  thereby  performs  the  same  function  that  a  train  in  the 
section  would. 

In  Fig.  22,  H  and  F  are  normally  clear  home  signals  protect- 
ing the  respective  insulated  track  sections,  5,  4,  3,  2,  and  1.  The 
reason  for  such  a  division  of  a  block  is  to  increase  the  reliability 
of  the  track  circuits  by  decreasing  the  effect  of  the  track-circuit 
current  leakage  from  rail  to  rail.  The  track  batteries,  G,  are 
connected  to  the  west  or  extreme  end  of  each  section,  so  that  a 
train  moving  in  the  direction  of  the  arrows  will  shunt  the  relays, 
the  batteries  discharging  their  current  through  the  entire  length 
of  the  rails.  This  protects  against  broken  rails  or  open  bonds, 


by  depriving  the  relays,  such  as  J,  E,  C,  A,  and  Z),  of  current 
when  such  an  open  circuit  occurs. 

Under  normal  conditions,  when  neither  of  the  sections  is  occu- 
pied by  a  train,  the  main  batteries,  as  R,  are  in  closed  circuit 
with  the  signal  mechanism,  thus  holding  the  discs  in  the  clear 
position.  When  a  train  is  approaching  a  signal,  it  is  not  affected, 
as  the  control  functions  remain  the  same.  After  entering  the 
block,  however,  the  relay,  J,  at  the  first  section  is  deenergized, 
thus  allowing  its  armature  to  fall,  and  open-circuiting  the 
signal  or  working  circuit  and  throwing  the  disc  (or  sema- 
phore) to  stop.  This  will  occur  on  any  section  within  the  block, 
as  the  armatures  and  contacts  are  in  series. 

The  functions  introduced  in  a  normal  danger  system,  which 
clears  the  semaphore  when  the  train  enters  the  preceding  block 
and  causes  it  to  remain  clear  until  the  train  has  left  the  block, 
irrespective  of  the  number  of  sections  it  contains,  are  set  forth 
in  the  diagram,  Fig.  23.  When  the  lower  or  back-contact 
armatures  or  points  of  relays,  M ,  W,  or  T,  drop,  the  home  sema- 


SIMPLE  CIRCUITS 


21 


phore,  V,  will  move  to  clear,  providing  the  front  contacts  of  K 
and  L  are  closed.  This  occurs  by  reason  of  the  back  contacts 
of  the  relays,  M,  W,  and  T,  at  sections  3, 4,  and  5  being  connected 
in  multiple,  so  that  if  one  back  contact  closes,  the  same  electrical 
condition  is  set  up  that  would  be  the  case  if  all  or  any  other  one 
of  these  contacts  were  closed.  The  front  contacts  of  these  relays 


ft^lL    A 


-2J 


t 


M 


a 


H'I'K 


r? 


FIG.  23 

are  in  series  with  the  main  battery,  7,  which  operates  signal 
P,  so  that  if  either  be  open,  the  signal  will  remain  at  danger;  a 
condition  occurring  when  a  train  occupies  either  section.  These 
relays  thus  become  double  functioned;  and  it  frequently  is  pos- 
sible to  have  all  the  contacts  at  a  section  box  controlled  by  one 
relay.  A  modification  or  extension  of  this  arrangement  is  used 
in  all  normal  danger  non-polarized  line-wire  systems. 

In  Fig.  24,  1  and  2  are  two  independent  normal  danger  home 
signals,  giving  indications  for  trains  bound  west.    The  cut  sec- 


FIG.  24 

tions,  7,  8,  9,  10,  and  12,  are  connected  to  the  respective  relays, 
S,  V,  R,  P,  and  Q,  whose  armatures,  with  one  exception,  close 
the  circuits  to  which  they  are  connected  when  the  relays  are 
energized.  The  lower,  or  back  contact,  armature  prong  on  R  is 
normally  open,  and  consequently  keeps  the  main  battery  in  open 
circuit.  Its  purpose  is  to  hold  the  semaphore  at  stop  when  R 
is  energized,  and  to  clear  the  blade  when  R  is  deenergized.  This 


22 


AUTOMATIC  BLOCK  SIGNALS 


latter  will  occur  only  when  a  train  occupies  section  9,  which  may 
thus  be  termed  a  setting  action.  This  clearing  of  the  sema- 
phore takes  place  under  restricted  conditions.  If  a  train  or 
broken  rail  occur  in  sections  7  or  8,  1  cannot  be  cleared  by  this 
armature  falling,  since  the  front  contacts  of  either  S  or  V  will 
be  open.  Thus,  if  a  train  occupy  section  8,  the  circuit  will  be 
opened  at  the  armature  of  relay,  V.  The  line  wires,  Y,  are  placed 
upon  poles,  and  pass  from  one  relay  to  the  others.  This  arrange- 
ment is  somewhat  similar  to  the  preceding,  with  the  exception 
that  the  home  signal  is  cleared  only  at  the  setting  section. 

Another  simple,  normal,  clear  home  and  distant  (on  the  same 
mast)  scheme  of  connection  is  shown  in  Fig.  25.  The  signals, 
T  and  P,  each  protect  the  track  for  two  blocks,  and  are  operated 
by  the  relays,  Q,  W,  B,  0,  and  M,  each  having  two  armature 


contacts,  the  lower  of  which  are  connected  to  the  distant 
blades,  and  the  upper  to  the  home  blades.  The  home  sema- 
phore at  P  is  controlled  through  the  armatures  of  relays,  B,  W, 
and  Q,  which  are  connected  to  sections  3,  4,  and  5.  The  dis- 
tant is  in  series  with  the  normally  closed  armatures  of  0  and  M 
at  sections  1  and  2.  These  relays  and  semaphores  are  inter- 
connected by  line  wires,  as  7  and  8.  It  will  be  noted  that 
the  relays  and  track  batteries  are  connected  to  opposite  ends 
of  each  section,  thus  requiring  the  relay  energizing  current  to 
pass  along  the  rails,  neutralizing  the  effect  of  fall  in  potential, 
and  assuring  the  positive  shunting  of  the  relay  by  the  train;  at 
the  same  time  guarding  against  broken  rails. 

The  two  general  methods  of  throwing  a  signal  member  to 
danger  when  there  is  an  open  switch  in  the  block  are  shown  in 
Fig.  26.  At  sections  8  and  10  we  have  two  switches,  at  which  are 
placed  the  switch  instruments,  B  and  F.  When  the  switch  at 


SIMPLE  CIRCUITS 


23 


8  is  opened,  B  short-circuits  the  track,  and  consequently  the 
relay  and  track  battery,  thus  setting  up  a  condition  analogous 
to  that  of  a  train  in  the  section,  the  signal,  K,  being  thrown  to 


—  to  signal 


main  track 


FIG.  26 


stop  in  this  case  by  the  deenergization  of  D.  This  is  effected 
by  contacts  within  the  switch  instrument  box  which  are  con- 
nected to  the  rails  of  the  track,  so  that  when  a  revolving  or 
rocking  member  is  operated  by  a  switch  point,  the  rails  become 
connected  electrically. 


24 


AUTOMATIC  BLOCK  SIGNALS 


At  section  10,  another  arrangement  is  employed.  F  is  a 
normally  closed  contact-spring,  which  is  in  series  with  the  main 
battery,  H,  contacts  of  E,  G,  and  /,  and  the  home  line  of  N. 
When  the  switch  is  thrown,  F  is  opened,  thus  causing  N  to 
assume  the  danger  position.  Such  a  device  is  used  only  in  line- 
wire  systems,  and  particularly  on  normal  danger  circuits. 

At  P,  the  switch  instruments,  T,  are  applied  to  a  cross- 
over; or  from  one  main  track  to  the  other  (trains  moving  in 
opposite  directions),  V  and  X  are  indicators,  whose  functions 
will  be  described  later.  Battery  C  supplies  current  to  relay  J, 
which  current  is  cut  off  and  the  track  rails  short-circuited,  when 
the  switch  is  thrown.  At  F,  the  same  arrangement  is  applied 
to  a  siding,  S  and  U  being  switch  instruments,  and  W  an 
indicator. 


FIG.  27 

A  simple  arrangement  of  overlap  circuits  in  which  distant 
signals  are  not  used  is  shown  in  Fig.  27.  Overlap  was  used  in 
most  early  systems,  to  give  an  indication  of  a  block's  condition 
prior  to  the  arrival  of  a  train  at  the  entrance  of  this  block,  thus 
eliminating  the  speed  reduction  that  would  be  otherwise  neces- 
sary in  case  a  fog  or  other  obscure  condition  prevented  a  clear 
view  of  the  signal.  The  block,  L-N,  consists  of  two  sections, 
L-M  and  M-N;  in  the  latter  an  open  switch,  K,  being  present. 
Signal  71  protects  this  block,  and  is  placed  between  signals  61 
and  81. 

The  signal  electromagnet,  S,  is  in  series  with  the  armatures, 
H  and  7,  of  relays,  F  and  G;  main  battery,  E;  and  switch  instru- 
ment, J,  at  switch,  K.  Since  the  latter  is  open,  E  cannot  dis- 
charge current  into  S,  because  of  the  open  circuit  at  the  switch 


SIMPLE  CIRCUITS  25 

instrument.  Due  to  the  rails  at  K  short-circuiting  the  section, 
M-N,  G  is  also  short-circuited,  and  its  armature  is  in  the  lower 
position.  F,  however,  is  still  energized  by  the  track  battery,  D, 
but  does  not  affect  S.  As  H,  E,  and  A  are  in  series,  the  arma- 
ture, B,  of  the  latter  closes  its  contact  and  allows  the  track  bat- 
tery, Ct  to  maintain  a  difference  of  potential  across  the  rails  of 
the  section  before  L-M,  or  the  second  section  of  signal  61. 

If  a  train  were  to  occupy  L-M,  A  would  be  deenergized,  thus 
holding  61  at  danger.  Also,  if  M-N  is  occupied,  71  will  be  at 
danger,  while  61  is  at  clear.  Signal  81  is  unaffected  by  train  or 
switch  movement  in  the  block  protected  by  71,  but  operations 
in  the  block  of  81  would  affect  71  in  the  manner  above 
shown. 

Overlaps  may  have  application  equally  well  to  normal  clear 
or  normal  danger  systems.  Figs.  28  and  29  show  the  circuits 
used  in  a  line-wire  system  for  overlap  on  a  single  track  for  the 
former,  with  home  signals  only.  Should  a  train  occupy  the  sec- 
tion between  161  and  162,  track  relay,  C,  will  be  deenergized, 
and  its  armature  contacts  consequently  opened.  This  open- 
circuits  the  clearing  magnet  or  slot,  H,  and  moves  162  to  danger. 
The  middle  armature  of  C  also  open-circuits  the  operating  mag- 
net of  161,  moving  the  latter  to  danger;  160  remains  cleared, 
however,  as  A  receives  current  from  the  battery  at  the  next 
signal  in  its  rear  (in  the  same  direction)  through  the  line. 

E  and  F  are  circuit  breakers  operated  by  the  moving  to  stop 
of  163,  and  /  is  an  indicator  placed  at  the  switch,  K,  in  series 
with  F.  Hence,  when  F  is  closed,  /  should  be  at  clear,  since 
it  receives  battery  current  from  B  (through  J"  and  K).  L  is 
another  switch  indicator  in  series  with  circuit  breaker,  M,  of  161. 
The  remainder  of  the  circuit  is  a  repetition  of  the  above. 

At  1,  in  Fig.  30,  L  is  a  switch  indicator  placed  at  the  main-line 
switch,  D,  which  will  indicate  clear  to  a  brakeman  only  when  the 
home  signals  in  the  two  preceding  blocks,  A  and  B,  are  at  clear. 
This  is  effected  through  the  use  of  circuit  controllers  or  relay- 
armature  front  contacts  at  these  signals,  as  shown.  At  2,  G  is 
a  polarized  instrument  which  consequently  has  two  (or  three) 
indication  positions.  The  controller  at  signal  E  determines  the 
setting  up  of  current  in  G,  and  the  pole  changers  at  F,  the 
polarity  of  this  current.  In  this  fashion,  the  banner  of  G  may 
either  be  in  a  central  or  side  position,  the  language  to  the 


26 


AUTOMATIC  BLOCK  SIGNALS 


brakeman  being  effected  by  its  moving  before  one  or  more 
apertures  in  the  mechanism  housing. 


=B 


i 

*5 


1 


Crossing  signals  are  employed  to  warn  pedestrians  or  teams 
at  a  highway  or  grade  crossing  of  the  approach  of  a  train  or  loco- 
motive. Fig.  31  shows  a  common  circuit  arrangement  for  such 


SIMPLE  CIRCUITS 


27 


a  scheme,  two  insulated  and  bonded  sections  of  track  adjacent 

MJ 


to  a  highway  forming  part  of  the  control  elements,  although  line 
wires  may  also  be  used.    These  sections,  1  and  2,  are  electrically 


28 


AUTOMATIC  BLOCK  SIGNALS 


isolated  by  the  insulating  joints,  G,  and  energized  by  the  track 
batteries,  A.  At  the  highway  a  signal,  3  (which  contains  the 
accessories  diagrammatically  shown),  gives  warning  of  train 


FIG.  30 


movement  by  the  ringing  of  a  bell;  which  latter  is  sometimes 
supplemental  to  a  small  low- voltage  incandescent  lamp  for  night 


FIG.  31 


indications.  L  is  a  station  or  block  tower,  provided  with  an 
automatic  drop,  H,  containing  an  audible  or  visual  indicating 
device,  J,  introduced  in  a  local  circuit  closed  by  the  release  of 


SIMPLE  CIRCUITS  29 

the  contact  armature.  E  is  a  relay  having  two  interlocking 
armatures  and  separate  magnets,  so  that  if  a  train  begins  moving 
in  either  direction,  the  bell,  F,  will  ring,  but  as  soon  as  it  passes 
the  highway,  F  will  cease  to  ring,  due  to  the  interference  of  the 
armature  prongs  which  hold  open  the  bell  circuit.  Thus,  sup- 
pose a  train  moves  from  1  to  2.  A  will  be  short-circuited  and  E 
deenergized,  allowing  a  current  to  flow  from  B  through  F.  At 
the  first  stroke  of  the  bell  clapper,  a  shunted  current  passes  over 
the  lines,  K,  and  thereby  operates  /.  As  soon  as  the  train 
passes  the  highway,  the  armatures  of  E  and  W  interlock,  one 
holding  the  other  away  from  the  common  contact,  thus  open- 
circuiting  F.  When  the  train  passes  out  of  section  2,  E1  is  ener- 
gized, thus  retaining  both  armatures  from  interference. 


CHAPTER  III. 
NORMAL  DANGER  CIRCUITS. 

IN  the  normal  danger  system,  the  indication  members  are 
always  in  the  danger  position,  except  when  a  train  is  approach- 
ing them.  In  the  last  chapter,  a  number  of  such  simple 
circuits  were  taken  up,  hence  preliminary  details  will  be 
unnecessary. 

Figs.  32  to  35  show  consecutive  normal  danger  line-wire  sig- 
nal circuits  as  applied  to  a  single-track  line  with  a  passing  side 


FIG.  32 

track,  and  trains  running  in  both  directions.  The  signals  are 
numbered  according  to  miles  and  tenths  of  a  mile,  indicators 
being  included  at  a  siding.  In  Fig.  32,  6  is  the  switch  leading 
into  the  main  siding,  while  4  is  a  track  relay  having  four  sets  of 
armature  contacts 

Should  a  train  be  approaching  127.2  (on  the  main  track), 
the  four-ohm  track-relay,  4,  will  be  short-circuited,  thus  causing 
all  of  its  contacts  to  open  except  the  second,  which  is  a  back 

30 


NORMAL  DANGER  CIRCUITS 


31 


contact.  The  closing  of  this  latter  causes  a  current  to  flow 
through  the  clearing  arrangement,  7,  main  127.2  line,  lower  con- 
tact at  6,  and  main  battery  at  the  preceding  section,  thus  clear- 


32 


AUTOMATIC  BLOCK  SIGNALS 


ing  127.2.  The  controllers,  8  and  9;  which  are  operated  by  the 
semaphores  at  this  signal,  are  in  series,  so  that  when  either 
operates,  line  10  is  open-circuited.  The  track  battery,  5,  is  con- 
nected to  both  the  main  and  siding  sections  by  the  cross  bond 
and  insulating  joint  at  6;  so  that  should  a  train  be  upon  either 
track,  it  will  be  short-circuited. 

In  Fig.  33,  12  is  a  track-relay  receiving  current  from  11,  the 
latter  also  energizing  the  section  constituting  the  end  of  the 
side  track.  The  switch,  13,  leading  into  this  siding,  operates 


/2S.2 


1 26.1' 

FIG.  34 

four  independent  contacts,  which  are  in  series  with  the  various 
line  wires.  The  main  battery  and  clearing  magnets  at  signals 
126.2  and  126.3  are  connected  to  the  common  line  wire,  while 
14  and  15  perform  functions  similar  to  8  and  9. 

Supposing  that  a  train  approaches  signal  125.2,  in  Fig.  34, 
17  will  be  short-circuited,  thus  closing  the  middle  armature  con- 
tact and  clearing  the  signal  through  18,  by  way  of  the  common 
wire,  line  125.2,  first  contact  of  19,  first  contact  of  20,  lower 
contact  at  22,  14,  15,  third  contact  of  12,  first  contact  of  23, 
battery  28,  and  returning  to  common. 

In  Fig.  35,  24  is  an  indicator  wound  to  800  ohms  resistance 
which  is  connected  to  the  indicator  line-wire  through  the  fourth 
armature  of  track  relay  25  (of  4  ohms  resistance),  to  the  first 
armature  of  17,  to  16,  middle  armature  of  19,  first  armature  of 


NORMAL  DANGER  CIRCUITS 


33 


26,  battery,  and  common  line.    The  remainder  of  the  connec- 
tions are  similar  to  those  just  considered. 


JJ 


JJ 


TO 


<0-=-<0 


/2V. 


MO* 


FIG.  35 


In  Figs.  36  and  37  the  connections  of  a  home  and  distant 
system  for  single-track  with  train  movements  in  one  direction 


A 

m. 


G\  W 


HOT 


PI 


ILL 


_!JI3_ 


03 


Indicator  wire- 


FIG.  36 


are  shown.  At  signal  1,  D  controls  the  distant  semaphore,  and  H 
the  home  semaphore,  both  being  mounted  on  a  common  mast. 
A  and  B  are  track  relays,  A  having  two  armature  contacts,  and 


34 


AUTOMATIC  BLOCK  SIGNALS 


B  one.  F  is  in  series  with  the  common  line  and  armature  G. 
4  and  J  have  a  common  connection  to  line  12,  and  are  respectively 
connected  to  H  and  line  Hl,  while  L  is  operated  by  H  and 
controls  the  distant  blade.  With  a  train  approaching  3,  B  and 
K  will  be  deenergized;  hence  J  will  be  opened,  and  M  closed, 
0  being  disconnected  from  H1  at  both  J  and  P. 

When  the  block  of  3  is  clear,  Q  and  R  will  be  closed.  T  is 
in  series  with  H  and  M  at  3,  and  D  at  1,  through  line  Dl.  R, 
S,  and  V  are  in  series  with  the  indicators,  /  and  W  (Fig.  37), 
through  the  indicator  line-wire.  H3  transmits  current  from  Z 
by  way  of  the  switch  instruments,  Y  and  X,  and  contact  8. 


Indicator  -wire* 

FIG.  37 

At  signals  5  and  7,  a  similar  arrangement  of  circuits  is  evident, 
one  side  of  the  main  batteries  being  connected  as  usual  to  the 
common  line.  At  7,  a  single  normally  open  circuit-breaker,  (7, 
is  provided,  for  the  control  of  the  distant  head  only. 

Figs.  38  to  41  contemplate  consecutive  normal  danger  over- 
lap signals  such  as  are  in  use  on  the  C.  N.  0.  &  T.  single- 
track,  with  trains  running  in  both  directions;  protection  being 
afforded  against  both  rear-end  and  head-on  collisions.  In  Fig. 
38,  four  signals,  1,  4,  15,  and  17,  with  their  connections,  are 
shown.  Four  track  sections,  with  batteries  3,  2,  18,  and  16, 
and  two  relays,  7  and  6,  constitute  the  control  functions  in  this 
figure.  7  has  three  armatures,  13,  14,  and  12,  the  first  being 
connected  to  the  main  battery  5,  the  second  to  signal  4  through 


NORMAL  DANGER  CIRCUITS 


35 


a  line  wire,  and  the  last  to  a  battery  line.  Armatures  8,  9,  and 
10,  of  track  relay  6,  are  connected  respectively  in  series  with 
main  battery  11  and  the  common  line,  armature  12  and  signal 
15,  also  14  and  a  battery  line.  Thus  one  side  of  each  main 


FIG.  38 

battery  and  signal  is  connected  to  the  common  line,  this  apply- 
ing to  all  four  illustrations. 

Continuing  the  track  sections  and  line  wires  at  a  cut  section 
in  Fig.  39,  two  track  relays,  36  and  37,  have  armatures  (contacts) 
38,  39,  40,  and  41,  42,  43,  respectively;  while  44  and  45  are 
connected  as  in  the  preceding,  39,  43,  and  40,  42,  being  inter- 
connected in  series. 


FIG.  39 

In  Fig.  40  a  siding,  20,  with  switches,  21  and  22,  is  added, 
signals  19  and  23  being  placed  at  this  siding.  Track  relays  24 
and  25,  each  having  two  armatures,  27,  26,  and  28,  29,  are 
added  at  the  setting  sections,  their  connections  being  similar  to 
those  already  given.  Switch  instruments  are  not  shown  at  21 
and  22,  as  they  short-circuit  the  track  in  a  manner  similar  to  a 
train  at  these  points,  when  open. 


36 


AUTOMATIC  BLOCK  SIGNALS 


The  track  battery,  30,  in  Fig.  41,  is  in  series  with  the  armature, 
32,  thus  introducing  track  circuit  control.  Signal  34  receives 
current  from  battery  44  through  contacts,  41  and  29,  while  35 
is  operated  by  current  coming  similarly  over  its  line  wire.  The 


r  ?] 

27   26 

29 

FIG.  40 

main  battery,  33,  is  in  series  with  armature  contacts  31  and  an 
armature  in  the  preceding  block. 

Suppose  a  train  to  be  moving  toward  the  west  at  46  and  that 
switch  21  is  open.    47  will  be  short-circuited,  and  consequently 


f  51 


FIG.  41 

37  deenergized,  which  causes  42  to  fall,  and  holds  19  at  danger, 
notwithstanding  the  fact  that  two  sections  intervene.  As  25 
is  also  demagnetized,  23  is  held  at  danger  by  reason  of  the 
position  of  28,  while  29  open-circuits  44,  and  thus  deprives  34 
of  current. 


NORMAL  DANGER  CIRCUITS 


37 


Another  line-wire  arrangement  for  home  and  distant  on  the 
same  masts  for  one  of  the  tracks  of  a  double-track  line  is  shown 
hi  Figs.  42  and  43.  At  the  former,  1  is  the  distant  line,  2  the 
home,  3  the  common,  and  4  the  indication.  Track  relays  6  and 
12  have  a  resistance  of  4  ohms,  7  of  12  ohms,  and  8  and  13  of 
16  ohms;  each  of  these  having  two  sets  of  contacts.  At  section 
9,  for  example,  there  are  a  set  of  binding  posts,  25,  which  are 


FIG.  42 

mounted  on  the  lightning  arresters  and  connect  to  fuses.  16 
and  21  are  back  contacts,  while  15,  17,  18,  19,  20,  22,  23,  and 
24,  are  front  contacts.  9  and  14  are  track  batteries,  the  latter 
in  series  with  15,  and  therefore  in  open  circuit  when  a  train 
occupies  section  27.  The  short-circuiting  of  12  also  short-cir- 
cuits 13  through  back  contact  16,  the  latter  being  in  shunt  with 
13.  When  the  train  reaches  section  28,  however,  12  is  energized 
and  16  opened,  B  receives  current  from  14  through  the  axles 


38 


AUTOMATIC  BLOCK  SIGNALS 


of  the  train,  which  thus  act  as  a  single-pole  switch.    5  is  a  main 
battery,  10  the  distant  semaphore,  and  11  the  home. 

In  Fig.  43  much  the  same  circuit  disposition  exists,  an  indi- 
cator, 28,  and  two  single  contact  switch  instruments,  29  and  30, 
being  introduced  at  the  main-line  crossover  switches,  31.  Both 
of  these  latter  are  also  in  series  with  the  home  line,  2,  and  the 
semaphore  apparatus  at  33,  which  is  the  usual  practice  for  main- 
line switches,  so  that  when  either  is  open  the  home  blade  at  33 
will  be  held  at  danger.  One  side  of  all  main  batteries  and 
switch  indicators  is  connected  to  the  common  line.  The  dia- 


FIG.  43 

grammatic  arrangement  of  binding  posts  is  as  it  actually  occurs 
in  the  relay  boxes. 

A  circuit  arrangement  for  double-track  application  is  given 
in  Fig.  44.  Two  signals,  7  and  6,  the  latter  a  distant,  protect 
a  home  block  consisting  of  several  sections,  three  of  which  are 
represented;  the  second  containing  a  switch,  11.  There  are 
four  main  batteries,  1,  2,  3,  and  4,  which  are,  respectively, 
for  operating  the  home-signal  motor,  control  relays,  switch 
bells,  and  distant  signal  motor.  A  vibrating  bell,  10,  is  placed 
at  the  switch,  which  rings  and  consequently  gives  warning  not 
to  throw  the  switch  when  a  train  is  in  the  second  section  from 
the  latter.  If  the  switch  is  thrown,  however,  the  home  signal 


NORMAL  DANGER  CIRCUITS 


39 


moves  to  the  stop  position.  This  will  be  announced  when  the 
section  is  clear  by  the  continued  ringing  of  the  bell,  which  in- 
dicates, as  will  presently  appear,  that  the  signal  has  been  set. 


o> 


FIG.  44 


When  7  is  cleared,  the  contacts,  13,  will  be  closed,  thus  ringing 
10.  13  is  in  shunt  with  the  armature,  19,  of  track  relay,  12,  while 
the  armature  contacts,  18,  of  this  relay  are  in  series  with  relays 
15  and  27,  battery  2,  and  armature  23  of  the  track  section,  28, 
relay  5.  Two  line  wires  are  used,  and  track  circuit-control  is 


40  AUTOMATIC  BLOCK  SIGNALS 

also  effected  by  relays  8  and  14,  whose  armature  contacts,  26 
and  20,  are  in  series  with  the  track  batteries. 

Suppose  a  train  enter  section  28.  Armature  23  will  fall,  thus 
sending  a  current  from  2  through  15  and  27,  through  whose 
front  contact  armature,  24,  a  current  passes  from  4  to  the 
distant-signal  motor,  and  from  1  to  the  home-signal  motor,  by 
way  of  16.  The  latter  action  causes  the  home-circuit  control- 
ler, 13,  to  be  operated,  closing  the  circuit  of  battery  3  and  the 
bell  as  above  shown.  (If  more  than  one  switch  occurs  in  a 
section,  the  individual  bells  are  connected  in  multiple.) 

As  the  train  enters  the  first  section  of  6,  14  is  deenergized, 
and  4  is  disconnected  from  6,  due  to  the  action  of  the  front 
contact,  21,  even  though  24  be  closed.  At  the  same  time  22  is 
closed  and  20  disconnects  the  track  battery  from  5,  thus  main- 
taining 23  in  its  lower  position.  If  the  block  of  7  is  occupied 
or  dangerous,  5  does  not  control  27  and  15,  since  12  open-cir- 
cuits battery  2,  the  signals  both  remaining  in  the  stop  or  normal 
position,  and  thereby  hold  the  train. 

As  the  train  moves  into  the  first  section  of  7,  the  latter  is 
deprived  of  current  by  the  deenergizing  of  relay  12  (should  the 
block  be  unoccupied),  due  to  the  circuit  of  battery  1  being  opened 
at  18.  The  bell,  10,  continues  to  ring,  however,  until  the  train 
moves  out  of  this  section,  due  to  its  circuit  being  completed 
through  19,  which  is  in  shunt  with  13,  and  performs  the  same 
function.  When  a  train  has  indirectly  deprived  27  of  current 
its  lower  or  back-contact  armature,  25,  closes  an  auxiliary  circuit 
through  the  motor  of  6,  which  short-circuits  the  latter,  and, 
by  causing  the  counter  e.m.f.  of  the  armature  to  set  up  a 
heavy  current,  effectually  retards  the  semaphore,  preventing 
the  inertia  of  the  moving  parts  from  destroying  any  part  of 
the  system.  In  shunt  with  25  is  the  armature,  22,  of  relay  14, 
so  that,  when  a  train  occupies  the  first  section  of  6  and  a  second 
train  is  approaching,  the  retarding  circuit  will  be  closed  in  any 
case,  which  would  not  be  the  condition  if  27  were  energized  by 
the  closure  of  23. 

The  motor-control  relays  are  similarly  connected  for  both 
signals,  this  connection,  somewhat  modified,  being  shown  in 
Fig.  118,  Chapter  IX.  Relay  A  is  27  in  the  last  figure,  the  two 
armatures,  B  and  C,  being  connected  to  battery  D  and  a  sta- 
tionary contact,  F.  J  is  an  electromagnet  which  retards  the 


NORMAL  DANGER  CIRCUITS 


41 


motion  of  the  armature  by  having  a  soft  iron  disk  rotate  be- 
tween its  poles,  this  disk  being  fastened  to  the  armature.  E  is 
a  contact  piece  moved  by  the  semaphore's  movement,  and  con- 
nects in  an  evident  manner  7,  H,  G,  and  F,  at  various  parts  of 
its  stroke.  In  the  position  shown,  B  is  connected  to  the  motor, 
but  not  to  the  other  side  of  the  battery.  If  A  is  energized,  C 
will  connect  D  to  the  motor,  this  setting  the  latter's  armature  in 
motion.  When  E  has  passed  over  F,  D  is  still  connected  to  the 
motor  through  G  and  H.  When  E  reaches  the  end  of  its  stroke, 
/  is  connected  with  G,  and  a  current  passes  from  D  through  J, 
rapidly  bringing  the  armature  to  rest,  due  to  the  eddy  currents 


J        1    — 

—                        JJ 

ihd    ' 

L1 

N? 

c 

:= 

•i 
•  j 
j 

5 

n, 

r- 

UL< 

T\^2^ 

H 

'Ml 

V\ 

BBJ 

Pf 

i 

M  1 

^ 

3* 

I 

E: 
y 

1M'. 

i  i 

j 

-» 

^ 

—  < 

k    §          i 

'  s  1  ~~^> 

J 
=71 

Lr^ 

/"; 

Si 

com  mon 

\\i 

¥  ' 

S. 

"  y^  ^^                                            ^\ 

lY//sdisS     Jo-ma   2 

°+—crossCLrms   on  pole  —  »c 
FIG.  45 

I    b*                                    ^ 

^//i  or  a 

set  up  in  the  disk  and  also  to  its  friction  on  the  magnet 
poles. 

Fig.  45  is  a  delineation  of  a  home  and  distant  circuit  for 
single  track,  with  train  movement  in  one  direction.  A,  B,  and 
C  are  operated  when  the  home  semaphore  is  cleared;  A  being  in 
series  with  the  local  distant,  B  in  circuit  with  the  preceding  dis- 
tant, and  C  controlling  the  switch  indicator;  the  latter  being  at 
danger  when  the  home  is  at  clear;  E  being  the  indicator  battery. 
B  is  also  in  shunt  with  magnet  G}  whose  armature,  with  the  150- 
ohm  resistance,  F,  is  connected  to  the  common  line,  and  the 
home-actuating  mechanism,  H.  G  is  energized  with  the  distant, 
at  signal  0,  through  its  track-controlled  relay  armature.  Hence, 
H  is  energized  either  from  the  preceding  distant,  or  the  local 
battery,  J;  in  any  case  however  through  the  front  contact  of  the 


42 


AUTOMATIC  BLOCK  SIGNALS 


four-ohm  track-relay,  K,  the  back  contact  governing  the  home 
at  signal  2. 

Fig.  46  continues  the  above,  with  a  siding  added.  P  and 
M  are  switch  instruments,  whose  functions  are  to  short-circuit 
both  tracks,  with  an  open  switch ;  and  to  control  the  home  sema- 
phore at  signal  2.  N  and  0  are  indicators,  in  parallel,  which 
are  connected  to  both  common  and  indicator  lines.  The  main 
battery,  I,  operates  the  home  semaphores  at  2  and  3. 

Figs.  47  and  48  (etc.)  show  normal  danger  circuits  in  conjunc- 
tion with  all-electric  interlocking,  as  more  specifically  set  forth 
in  Chapter  XIV.  These  occur  at  Union  Street,  Allentown,  Pa., 
on  the  Lehigh  Valley  Railroad,  at  its  intersection  with  the 
Allentown  Terminal  Railroad;  and  in  addition  to  this,  several 
sidings  and  branch  lines.  The  working-circuit  network  emanates 


from  a  signal  cabin,  within  which  is  the  interlocking  machine 
and  its  accessories.  Three  separate  common  lines,  A,  B,  and 
C,  with  relay  control,  are  used.  Motor  armatures  are  designated 
by  A,  brake  magnets  by  BM,  and  signals,  switches,  and  derails 
by  numerals.  Dwarf  signals,  such  as  4,  18,  47,  etc.,  are  used 
subsidiary  to  main  and  branch-line  signals,  and  are  of  lesser  size. 
84  and  85  are  vibrating  bells  under  the  control  of  track  func- 
tions preceding  those  shown;  86  is  a  storage  battery;  87  a  west- 
bound distant  indicator  with  shunted  bell;  88  a  westbound 
track  indicator;  89  an  east-bound  track  indicator;  and  90  an 
east-bound  distant  indicator  with  a  bell  in  multiple;  931  and 


NORMAL  DANGER  CIRCUITS 


43 


932  are  disk  signals,  whose  "hold  clear"  coils  have  a  resistance  of 
600  ohms;  91  and  92  are  16-c-p.  110-volt  incandescent  lamps, 


44 


AUTOMATIC  BLOCK  SIGNALS 


controlled  by  signals  1  and  51  respectively,  and  form  a  visual 
indication  at  the  tower  of  movement  thereof. 


93,  94,  95,  etc.,  are  slot  magnets  which  allow  the  signal  arm 
to  return  to  stop  when  deenergized.     The  remainder  of  the  cir- 


NORMAL  DANGER  CIRCUITS 


45 


cuits  are  common  to  those  preceding,  or  will  be  more  compre- 
hensively evident  on  consulting  Chapter  XIV. 

In  Fig.  49  is  developed  a  normal  danger  three-position  signal 
circuit  for  six  consecutive  signals,  with  a  train  in  each  of  the 
blocks  of  K,  P,  and  S,  and  a  crossover  switch,  Y,  in  that  of  N. 
The  connections  at  all  of  the  blocks  are  similar;  with  the  excep- 
tions of  the  functions,  D,  E,  F,  G,  H,  and  J,  which  are  intro- 
duced for  variation.  Describing  the  apparatus  at  K,  we  have, 


indicator 


FIGS.  47,  48  (III) 

the  three-position  signal  relay,  3P,  track  relay,  T,  motor,  M, 
clutch-magnet,  C,  lock-magnet,  L,  main-battery,  B,  and  the  con- 
tact-arrangement, Z,  operated  by  3  P.  This  latter  changes  the 
interconnection,  so  that  at  each  indication  position  we  have  a 
proper  circuit-arrangement.  Three  stages  of  contacts  exist:  (1) 
when  the  semaphore  is  at  clear,  and  4  is  connected  to  5,  as  at  W; 

(2)  when  the  blade  is  at  normal  or  danger,  as  at  X  (a  similar 
condition  obtaining  when  the  arm  is  at  caution,  as  at  7);  and 

(3)  when  the  semaphore  is  at  danger  with  a  train  in  its  block, 
as  at  Z;  and  1  is  in  contact  with  2. 


46 


AUTOMATIC  BLOCK  SIGNALS 


It  should  be  noted  that  the  3P  relays  are  in  multiple  with 
the  succeeding  main  batteries  through  the  front-contact  arma- 
tures, U,  of  the  track  relays;  and  that  in  order  to  energize  the 


motor,  clutch,  and  lock  magnets  it  is  necessary  for  the  back  con- 
tacts, R,  of  the  preceding  relays  to  close.  This  energization 
will  not  occur  unless  all  other  conditions  are  normal,  an  impossi- 


NORMAL  DANGER  CIRCUITS 


47 


bility  if  the  track  is  short-circuited  or  open  by  any  cause.    The 
front  contact,  A,  of  the  3P  relays  is  for  energizing  the  lock 


-0          *f- 

4 

c 

,       * 

fc 

r 

* 

3 

I 

t 

S 

, 

-f 

cc 


magnets,  and  then  only  by  way  of  R  and  at  such  times  as  the 
motor  and  clutch  magnets  are  not  in  circuit.  In  this  case  three 
line  wires  are  necessary,  as  8,  9,  and  10. 


48 


AUTOMATIC  BLOCK  SIGNALS 


Fig.  50  gives  the  circuit  connections  peculiar  to  a  control 
scheme  for  semi-automatic  home;  advance,  and  distant  sema- 


phores.    The  home  blade,  N,  is  controlled  by  lever  1,  and  when 
the  latter  is  thrown,  contact  C  is  closed;  and,  if  D  be  then 


NORMAL  DANGER  CIRCUITS 


49 


momentarily  pressed  down,  B  will  be  energized  by  the  shunt- 
ing of  battery  L.  This  causes  a  current  to  pass  through  A,  pro- 
viding K  is  on  closed  circuit,  even  though  D  be  released.  When 
lever  2  is  thrown,  E  is  closed,  and  if  F  is  then  closed  for  a  moment, 


FIG.  50 


a  current  will  pass  through  the  low-resistance  winding  of  J  from 
battery  M.  This  raises  its  armature,  throwing  in  circuit  the 
high-resistance  winding  and  the  shunt-track  circuit  of  the 
distant  0,  energizing  G,  and,  in  the  proper  sequence,  H. 


CHAPTER  IV. 


NORMAL  CLEAR   CIRCUITS. 

IN  all  normal  clear  systems,  the  signal  semaphores  or  disks  are 
in  the  clear  position  at  all  times  except  when  a  train  is  in  the 
block  protected,  or  an  otherwise  dangerous  condition  exists. 
This  implies  that  the  clearing  or  retaining  devices  are  normally 
in  circuit  with  the  power  battery,  and  that  their  control  is 
primarily  effected  with  front  relay  contacts. 

In  Fig.  51  a  diagram  of  one  form  of  polarized  system  of  normal 
clear  signals  is  given.  C  is  a  two-arm  semaphore  signal,  E  being 


B 


J_    I    v 


FIG.  51 

the  distant,  and  F  the  home  blade.  F  indicates  the  condition 
of  block  A-B,  to  one  end  of  which  the  polarized  track  relay,  7, 
is  connected,  this  relay  deriving  current  of  a  given  polarity  from 
the  track  battery,  R,  at  B.  This  circuit  is  through  the  rails  of 
the  track  and  the  pole-changing  switch,  P,  which  is  actuated 
mechanically  (in  the  direction  shown  by  the  contacts)  by  the 
home  blade,  H,  of  signal  D. 

The  distant  blade,  G,  is  not  shown  connected,  to  simplify  the 
circuits;  while  the  pole  changer  is  omitted  at  C  for  the  same 
reason.  Relay  S  is  connected  across  section  V,  in  the  block 
controlled  by  H,  and  derives  current  from  a  battery  at  the 

50 


NORMAL  CLEAR  CIRCUITS  51 

other  end  of  this  block,  a  polarity  changer  being  also  inter- 
posed. 

Relay  S,  through  the  armature  T7,  and  a  front  contact,  con- 
trols the  flow  of  current  from  the  signal  battery  U,  to  the  home 
blade,  so  that  when  S  is  deenergized  T  falls,  and  by  opening  the 
circuit  of  U,  causes  H  to  move  to  the  danger  position. 

If  a  train  occupies  the  block  between  A  and  B,  R  will  be 
short-circuited,  thus  deenergizing  /  and  allowing  the  neutral 
armature,  K,  to  drop,  thereby  open-circuiting  the  signal  battery, 
M,  and  causing  F  to  move  to  the  danger  position.  0  is  a  series 
switch  open-circuited  mechanically  by  the  motion  of  F;  hence 
E,  deriving  current  from  M  through  this  switch,  moves  to  the 
caution  position. 

The  neutral  armature,  K,  is  connected  to  J  by  the  jumper 
wire,  N,  J  being  the  polarized  armature  of  7,  whose  direction  of 
motion,  and  consequently  of  contact,  depends  upon  the  polarity 
of  the  current  which  I  receives.  With  P  in  the  position  shown, 
J  will  be  in  contact  with  its  contact  finger ;  but  if  P  be  reversed, 
/  will  be  on  open  circuit.  This  latter  condition  will  evidently 
occur  if  a  train  be  in  section  V. 

When  the  train  passes  out  of  the  block  of  H,  it  moves  to  the 
clear  position,  by  the  action  of  relay,  S,  which  restores  current 
to  this  blade.  This  causes  a  shifting  of  the  pole  changer,  which 
returns  to  the  position  shown  in  the  diagram.  The  reversal  of 
polarity  causes  J  to  move  to  its  normal  position,  thus  restoring 
E  to  the  clear  position. 

Fig.  52  shows  diagrammatically  the  arrangement  of  a  block 
consisting  of  two  insulated  track  sections,  A-B  and  B-C;  the 
home  and  distant  semaphores  being  on  separate  posts.  Such 
an  arrangement  is  employed  where  the  blocks  are  of  considerable 
length,  and  wherever  it  is  most  desirable  to  locate  the  home  and 
distant  blades  on  independent  posts,  the  distant  semaphores 
being  placed  between  the  home  signals. 

Upon  a  train's  entering  the  section,  A-B,  the  armature,  H,  of 
track  relay  G  falls,  thus  open-circuiting  the  main  battery,  T, 
and  causing  D  to  move  to  the  danger  position.  When  the  train 
enters  the  section,  B-C,  the  track  relay  /  is  short-circuited,  thus 
allowing  its  armature,  J,  to  fall,  and,  by  open-circuiting  track 
battery  M,  depriving  section  A-B  of  battery  current.  Thus 
G  remains  deenergized  while  D  remains  at  the  danger  position. 


52 


AUTOMATIC  BLOCK  SIGNALS 


The  presence  of  the  train  in  section  B-C  also  allows  the  neutral 
armature,  K,  to  fall,  hence  E  moves  to  the  caution  position, 
being  deprived  of  current  from  the  main  battery,  S. 

ABC 


II 


H 


FIG.  52 

The  polarized  armature,  L,  is  not  directly  affected  until  the 
train  has  passed  the  insulating  joints  at  C,  when,  by  N  being 
short-circuited,  P  falls,  thus  moving  F  to  the  caution  position 
by  open-circuiting  the  main  battery,  0.  The  motion  of  F 
throws  the  polarity  reverser,  Q,  over,  thereby  reversing  the  po- 
larity connections  of  R  to  the  rails  of  section  B-C,  and  causing 
L  to  move  away  from  its  contact,  maintaining  E  in  the  caution 
position.  This  will  continue  until  the  train  passes  out  of  the 
section  controlled  by  F,  when  E  will  return  to  clear. 


FIG.  53 

The  consecutive  connections  of  home  and  distant  normal  clear 
signals  for  one  side  of  a  double-track  line  are  shown  in  Figs.  53 
and  54.  At  signal  1619,  D  operates  the  distant  blade  and  H 


NORMAL  CLEAR  CIRCUITS 


53 


the  home  semaphore.  In  reality,  these  are  motor-slot  magnets, 
the  motor  itself  being  operated  through  an  auxiliary  circuit, 
which  consideration,  however,  does  not  affect  the  fundamental 
connections.  A  and  B  are  closed  by  the  clearing  of  the  home 
board,  A  being  in  series  with  the  distant  at  1619,  and  B  in  series 
with  the  distant  at  1609  through  the  line  wire.  H  is  operated 
by  current  from  the  power  battery,  C,  through  the  armature  of 
track  relay  E.  Hence,  when  the  block  of  1619  is  occupied,  H 
will  be  deprived  of  current,  and  A  simultaneously  opened,  thus 
throwing  both  semaphores  to  the  stop  position. 

The  connections  at  1629  are  similar  to  the  above,  a  series 
relay,  F,  being  added,  however,  whose  armature  is  raised  when 


FIG.  54 

current  parses  to  the  switch  indicators,  G  and  7,  in  Fig.  54, 
through  the  common  and  indicator  line-wires,  armature  /  at 
1639,  and  battery  M.  The  remaining  circuits  at  1639  and  1649 
are  practically  identical  with  the  preceding.  In  both  dia- 
grams a  common  line-wire  is  introduced.  This  is  the  usual 
practice  with  line-wire  systems,  one  side  of  the  main  batteries 
and  switch  indicators  being  connected  to  it,  thus  economizing 
on  the  extra  copper  that  would  otherwise  be  required. 

In  Figs.  55  and  56,  2,  4,  6,  and  8  are  normal  clear  home  and 
distant  signals  controlled  through  line  wires  and  applied  to  one 
of  the  tracks  of  a  double-track  railroad.  But  one  track  relay 
is  used  in  each  block,  the  contacts,  C,  of  these  relays  being  in 
series  with  the  home  operating  device.  B  is  a  distant  contact 
in  series  with  the  circuit  breaker,  E,  operated  by  the  home  sema- 


54 


AUTOMATIC  BLOCK  SIGNALS 


phore  and  controlling  therewith  the  distant  blade  of  the  pre- 
ceding signal.  Track  circuit-control  is  introduced  at  T,  Fig. 
56,  this  arrangement  being  generally  interposed  in  long  blocks 


FIG.  55 

having  necessarily  several  sections.  The  front  contact  of  the 
relay,  T,  is  in  series  with  the  track  battery,  M,  the  back  contact 
being  in  shunt  with  the  latter.  Hence,  when  T  is  energized, 


line 


FIG.  56 


Jlf  will  be  connected  to  and  energize  section  N,  while  when  T 
is  deprived  of  current,  the  back  contact  will  short-circuit  the 
track  at  N,  the  front  contact  simultaneously  open-circuiting  M . 


NORMAL  CLEAR  CIRCUITS 


55 


At  the  switch,  G,  a  contact,  F,  is  arranged,  so  that  when  the 
switch  is  open  H  will  be  deenergized  and  the  home  and  distant 
blades  at  signal  2  thrown  to  stop.  One  side  of  each  of  the  main 
batteries,  7,  /,  K,  and  L,  is  connected  to  the  common  line-wire, 
as  in  the  preceding  case. 

Figs.  57  to  62  show  the  standard  normal  clear  overlap  line- 

LOCATION     PLAN 


WIRING    DIAGRAM 


FIG.  57 

wire  circuits  on  single-track  for  east-  and  west-bound  movements 
on  the  Southern  Pacific. 

In  Fig.  57,  A  and  5  are  distant  signals  indicating  the  track 
condition  when  approaching  a  station  siding.  The  location  plan 
shows  the  extent  of  the  sections  protected  by  the  semaphores 
and  the  arrangement  .of  the  signals.  Home  signals,  C,  D,  E, 
and  F,  are  operated  by  the  motors  and  accessories  having  cor- 
responding letters.  A,  for  example,  is  controlled  through  the 


56 


AUTOMATIC  BLOCK  SIGNALS 


armature  of  relay  H,  the  latter  being  connected  to  main  battery 
G  through  a  front  contact  of  track  relay  I,  and  the  normally 
closed  circuit  breakers  at  D  and  F,  by  way  of  one  of  the  distant 
line  wires. 

In  Fig.  58  a  similar  arrangement  is  employed,  a  cut  or  relayed 
section  being  introduced.  This  changes  the  extent  of  the  con- 
trol of  the  home  signal  preceding  J  in  the  location  plan,  and 

LOCATION      PLAN 


WIRING     DIAGRAM 

h 


FIG.  58 

interposes  a  track  relay,  K,  having  two  front  and  two  back 
contacts.  The  front  points  extend  the  function  of  the  home 
line  wires,  the  back  points  short-circuiting  L  and  connecting 
one  of  the  home  lines  to  common. 

In  Fig.  59  overlaps  are  introduced  at  the  west  end  of  a  station 
siding,  and  a  distant  signal  at  the  east  end.  -  The  distant  con- 
trol-line, M ,  is  in  series  with  the  home-circuit  controllers,  N  and 
0,  current  being  derived  from  the  main  local  battery,  P,  an 
independent  local  battery,  Q,  operating  the  mechanism.  It  will 


NORMAL  CLEAR  CIRCUITS 


57 


be  noted  that  the  negative  sides  of  the  main  batteries  are 
connected  to  the  common.  This  precludes  the  possibility  of 
dissimilar  polarity,  and  the  consequent  wasteful  discharge  on 
confusion  of  the  circuit  wires. 

The  converse  of  the  above  appears  in  Fig.  60,  a  distant  signal 
being  placed  at  the  west  end  (in  this  book,  the  east  is  always  at 
the  right  and  the  west  at  the  left  hand  side,  as  will  occur  when 

LOCATION       PLAN 


west 


east 


WIRING      DIAGRAM 


common' 

FIG.  59 

the  reader  is  facing  north),  and  overlap  at  the  east  end.  The 
independent  working  circuit  is  at  R  in  this  case,  relay  S  having 
three  front  and  two  back  points,  the  latter  connecting  to  com- 
mon. The  front  points  clear  the  signals  for  one  direction  of 
train  movement,  and  the  back  points  are  for  the  opposite  sense, 
also  completing  these  same  control  circuits. 

Figs.  61  and  62  show  the  circuit  arrangements  between 
stations,  with  overlap.  In  the  former,  home  signal  T  is  con- 
trolled through  line  1,  and  U  through  line  2.  The  working  ctr- 


58 


AUTOMATIC  BLOCK  SIGNALS 


cuit,  7,  of  the  former  is  independent,  that  of  the  latter  being 
connected  to  the  common,  as  are  all  the  track-relay  back  points. 
In  Fig.  62  a  relayed  section  only  is  shown,  the  line  wires  being 
simply  broken  at  the  relay  contacts,  a  location  diagram  being 
unnecessary  in  this  case.  As  before,  the  back  contacts  are 
connected  to  common,  and  close  the  preparatory  control 
functions. 


LOCATION       PLAN 


WIRING     DIAGRAM 

fc-  A 


FIG.  60 


Figs.  63  to  66  show  normal  clear  motor-circuits  and  signal 
arrangements  on  the  Missouri  Pacific,  the  mile  posts  and  signals 
being  numbered  from  the  terminal  at  St.  Louis.  Home  and 
distant  semaphores  are  placed  on  separate  masts  and  controlled 
through  line  wires.  The  motor  connections  only  are  represented, 
but  of  course  slot  magnets  are  in  parallel  with  the  main  bat- 
teries, the  motors  not  being  in  circuit  except  when  clearing  takes 
place. 


NORMAL  CLEAR  CIRCUITS 


59 


At  home  signal  142,  a  circuit  controller  is  introduced,  which 
closes  the  track  relay  upon  itself  when  the  switch  is  thrown, 

LOCATION      PLAN 


X>    )// 


WIRING     DIAGRAM 


1 

J- 

4  i 

4 

common 

FIG.  61 


and  connects  the  relay  to  the  track  when  the  switch  is  returned. 
In  the  semaphore's  stop  position,  also,  a  circuit  breaker  in  series 


BTTQ 


cM1 


FIG.  62 


with  the  motor  at  the  distant  signal,  142-D,  is  closed,  clearing 
the  latter  by  energizing  the  motor  relay. 


60 


AUTOMATIC  BLOCK  SIGNALS 


NORMAL  CLEAR  CIRCUITS 


61 


62 


AUTOMATIC  BLOCK  SIGNALS 


NORMAL  CLEAR  CIRCUITS 


63 


-a 
««i 


64 


AUTOMATIC  BLOCK  SIGNALS 


The  track  relays  at  172  and  171  have  four  sets  of  contacts 
each,  three  of  these  being  for  the  line  wires;  thus  constituting 
simultaneous  quadruple  breaks  (one  for  each  track  section) 
in  these  lines,  which  pass  to  preceding  and  succeeding  signals. 
At  Valley  Park  two  sidings  appear,  for  train  movement  in  both 
directions.  Signals  191  and  202  each  have  a  circuit  controller 
and  breaker,  which  control  the  track  relay  and  section  and  the 
distant  signal  of  each  respectively.  At  Castlewood  a  single 
siding  is  introduced,  the  signal  and  connection  arrangements 
being  similar  to  the  preceding.  It  will  be  noted  that  the  motor 
batteries  are  not  connected  to  the  common  line,  since  they  are 
part  of  independent  local  working-circuits.  The  lengths  of  the 
various  sections  may  be  approximated  from  the  mile  posts. 


The  wiring  for  a  one-arm  distant  in  an  overlap  system  is 
shown  in  Fig.  67,  —  the  diagrammatic  scheme  of  connection 
being  represented  at  A,  NP  is  a  neutral  and  polarized  relay 
(commonly  termed  simply  a  polarized  relay) .  The  circuit  con- 
troller, Kj  operated  by  the  semaphore,  is  in  series  with  the 
motor  and  low-resistance  (or  compounding)  winding,  L,  of  the 
slot  magnet.  The  high  resistance  winding,  //,  is  connected  to  N 
and  the  front  armature  contacts,  normally  holding  the  signal 
blade  at  clear.  The  track  battery,  T,  is  divided  into  two  parts, 
which  are  in  series  and  have  a  common  junction,  IT.  When  one 
of  the  neutral  front  contacts  is  closed,  two  cells  in  multiple  are 
connected  across  the  track,  of  a  certain  polarity;  and  when 
the  back  contact  is  closed,  but  one  cell,  of  opposite  polarity. 


NORMAL  CLEAR  CIRCUITS 


65 


In  Fig.  68  the  connections  of  a  normal  clear  home  semaphore, 
with  a  separate  distant  in  the  rear,  appear.  The  use  of  a  slow 
releasing  relay  admits  of  an  ordinary  slot  magnet,  S,  having  as 
usual  a  compound  winding.  The  track  relay,  R,  has  four  ohms 
resistance,  and  is  of  the  ordinary  neutral  type.  T  is  connected 
to  the  block  preceding  the  home  signal  through  the  polarity 
reverser,  P.  The  armature  and  front  point  of  the  slow  releasing 
relay  are  in  series  with  the  motor  and  low-resistance  winding 
of  the  slot,  this  relay  being  connected  across  the  main  battery, 
Q,  through  the  front  points  and  armature  of  R.  N  is  a  circuit 


FIG.  68 

breaker  in  series  with  the  motor,  and  breaks  the  continuity  of 
the  working  circuit  when  the  semaphore  is  at  full  clear. 

The  relay  and  signal  connections  for  a  single-track  normal 
clear  two -arm  home  and  distant  arrangement  are  shown  in  Fig. 
69.  The  polarity  reverser,  R,  operated  by  the  home  signal,  is 
connected  to  the  track  and  track  battery,  T,  thus  controlling 
section  S  of  the  preceding  distant  semaphore  circuit.  The  arma- 
ture and  front  contacts,  A  and  F,  of  the  slow  releasing  relay, 
K,  are  in  series  with  the  home  slot,  HS,  and  motor,  and  con- 
nected to  the  latter  through  the  contact  springs,  A,  which,  with 
B  and  C,  are  operated  by  the  home  blade.  D  is  operated  by 
the  distant,  and  with  A  is  normally  open.  Plate  G,  at  the 


66 


AUTOMATIC  BLOCK  SIGNALS 


fuse  and  arrester  blocks,  is  connected  to  ground.  The  neutral 
and  polarized  track-relay  has  two  front  and  two  back  con- 
tacts, the  diagrammatic  circuit-arrangement  being  as  shown  in 
Fig.  51. 


FIG.  69 

A  standard  circuit  arrangement  for  a  normal  clear  wireless 
single-arm  home  signal  is  shown  in  Fig.  70.    A  slow  releasing 

N 


FIG.  70 

slot,  P,  which  eliminates  a  separate  slow  releasing  relay,  is  con- 
nected to  the  common  wire  and  the  armature  of  the  four-ohm 
track-relay,  T,  being  in  shunt  with  the  motor,  M .  The  latter 


NORMAL  CLEAR  CIRCUITS 


67 


is  in  series  with  N  and  operates  when  the  latter  is  closed, 
which  is  the  case  whenever  the  semaphore,  S,  is  not  at  full  clear. 
The  polarity  reverser,  V,  governs  the  distant  of  S  through  the 
polarized  relay.  In  series  with  the  magnets  of  T  are  the  light- 
ning arresters,  R,  the  plate  beneath  which  being  connected  to 
ground.  The  main  binding  posts  and  fuse  strips  are  shown  at 
D,  to  which  all  incoming  and  outgoing  wires  are  connected. 

A  normal  clear-wiring  diagram  for  a  one-arm  home  sema- 
phore with  overlaps  is  shown  in  Fig.  71.    The  slow  releasing 


FIG.  71 

relay,  K,  is  connected  as  already  described,  but  a  polarity  rever- 
ser is  not  used.  Instead,  the  polarized  relay,  P,  has  an  addi- 
tional neutral  back-contact  and  armature,  which  short-circuits 
the  track  upon  its  deenergization.  In  the  upper  or  working 
position  this  armature  connects  the  battery  to  the  track  section 
protected  by  the  preceding  semaphore.  The  scheme  of  con- 
nection used  will  be  rendered  clearer  by  the  inspection  of  the 
small  diagram  at  7 la. 


FIG.  7la 


CHAPTER  V. 
SEMI-AUTOMATIC  CIRCUITS. 

A  SEMI-AUTOMATIC  signal  is  one  having  automatic  appurte- 
nances, but  controlled  from  a  manually  operated  signal,  cir- 
cuit controller,  or  similar  devices.  These  are  most  frequently 
used  in  connection  with  interlocking  or  manual  signal  towers, 
and  constitute  either  an  adjunct  or  an  extension  of  the  latter. 
Manual  signaling  cannot  be  effected  over  any  great  length  of 
track  on  either  side  of  a  cabin;  hence  semi-automatic  distant 
signals  have  been  applied  to  most  of  such  cases. 

An  interlocking  plant  having  mechanical  fixtures  with  elec- 
trical control,  may  frequently  be  combined  with  an  automatic 
section.  Fig.  72  illustrates  such  a  composite  arrangement,  with 


FIG.  72 

a  mechanical  signal  at  danger,  and  a  home  and  distant  auto- 
matic signal  protecting  the  block  immediately  preceding  the 
former.  N  is  &  polarized  track  circuit  relay,  and  G  is  a  neutral 
relay.  When  the  track  section,  S,  is  in  its  normal  condition,  and 
the  mechanical  signal  is  at  danger,  the  neutral  relay,  A,  is  dee'n- 
ergized,  hence  its  back  armature  contacts  control  the  track 
polarity.  Relay  N  receives  a  current  of  this  polarity,  and  its 
neutral  armature  closes  the  circuit  of  the  main  signal  battery, 
/,  thus  sending  a  current  through  L  and  holding  it  at  clear. 

When  the  home  signal,  P,  is  cleared,  the  circuit  controller,  B,  is 
closed,  which  raises  the  armature  of  D,  thus  closing  the  circuit 

68 


SEMI-AUTOMATIC  CIRCUITS 


69 


of  C  and  sending  a  current  through  A.  This  reverses  the 
polarity  of  the  track,  and  closes  the  polar  contact,  H,  which 
throws  M  to  the  clear  position,  by  sending  a  current  from  / 
through  J,  H,  K,  M,  and  7.  The  controller,  K,  is  operated  by 
motion  of  F,  it  being  thus  necessary  for  the  home  semaphore  to 
clear  first.  The  momentary  cessation  of  current  produces  no 
effect  upon  the  home  automatic  blade,  because  it  is  equipped 
with  a  slow  releasing  slot  or  magnet.  This  retardation  of  move- 
ment is  produced  by  using  in  N  a  solenoid  of  high  self-induction, 
wound  upon  copper  tubes,  which  thus  opposes  any  rapid  change 
in  the  magnetic  flux.  G  has  a  relatively  high  resistance,  so 
that  when  a  train  enters  the  section,  S,  it  controls,  it  will  open 
the  circuit  of  A  and  D.  Hence  the  armature  of  D  must  be 
returned  to  its  upper  position  when  A  has  been  energized,  in 


n*  ,    ru  , 


FIG.  73 

order  to  close  the  circuit  of  C.  Thus  every  train  movement 
requires  that  the  operator  raise  the  armature  of  D,  otherwise 
danger  indications  will  be  given.  F  and  M  thus  operate  auto- 
matically when  the  mechanical  signal,  P,  is  properly  manipu- 
lated. 

Frequently,  a  distant  signal  must  be  operated  after  several 
home  signals  have  been  cleared.  For  this  purpose  a  device, 
erroneously  termed  a  commutator,  is  placed  upon  each  home 
signal  in  such  a  series.  This  consists  merely  of  a  make  and 
break,  similar  to  a  controller.  A  series  of  this  kind  is  shown  in 
Fig.  73;  B,  F,  and  7  are  commutators,  which  are  fastened  to  the 
masts  of  the  home  signals,  A,  E,  and  77,  respectively.  D  is  an 
interlocking  lever,  which  controls  through  G  the  electrical  func- 
tions, and  is  dependent  on  the  positions  of  the  contacts  of  the 
commutators.  The  local  circuit,  J,  of  the  distant  signal,  M,  is 


70 


AUTOMATIC  BLOCK  SIGNALS 


controlled  by  the  line  relay,  P,  which  is  actuated  by  the  main 
battery,  C.  It  is  evident  that  there  may  be  any  number  of 
similarly  connected  home  signals  in  such  a  system.  -  . 

In  Fig.  74  a  circuit  controller  is  connected  mechanically  to 
the  lever,  A,  for  the  purpose  of  controlling  the  current  from  the 
battery,  B,  the  latter  having  in  circuit  the  commutator,  G,  on 


a 


/>H      | 


FIG.  74 

the  cleared  mechanical  home  signal,  H,  and  a  line  relay,  P.  The 
armature,  C,  of  the  latter  alternately  connects  and  disconnects 
the  track  battery  at  H  from  the  track  relay,  E,  controlling  the 
distant  signal,  D,  short-circuiting  the  section,  S,  in  its  lower  or 
back-contact  position.  Current  is  passing  through  the  three 
circuits,  both  signals  therefore  being  in  the  clear  position. 

In  order  to  shunt  the  contacts  of  a  relay,  so  that  a  control 
outside  of  that  produced  by  the  energizing  of  the  relay  under 
operative  conditions  can  be  effected,  a  spring  key  is  used.  The 
circuit  arrangement  in  Fig.  75  utilizes  such  a  device.  Across, 


1 


n  H  | 


FIG.  75 

or  in  shunt  with,  the  upper  armature  of  the  magnetic  circuit- 
controller  and  indicator,  D,  the  spring  key,  B,  is  connected. 
The  lower  armature  is  connected  across,  and  thus  short-circuits 
the  track  in  its  lower  position,  and  connects  the  track  to  the 
battery,  E,  in  its  upper  position.  C  is  a  circuit  controller 
closed  by  the  clearing  of  the  home  signal,  H,  and  is  in  series 


SEMI-AUTOMATIC  CIRCUITS 


71 


with  D.  E  energizes  the  track  relay,  A,  at  the  distant 
signal,  J. 

When  B  is  pressed  downward,  and  C  is  closed  by  clearing  the 
home  signal,  a  current  passes  through  D  which  lifts  its  arma- 
tures, the  upper  one  maintaining  the  current  initiated  by  B, 
and  the  lower  one  sending  a  curreYit  through  A,  thus  clearing  J. 

Fig.  76  represents  a  scheme  of  connections  introducing  a  com- 
bined indicator  and  magnetic  circuit  controller  into  the  circuit 
of  the  line  relay,  P.  This,  given  at  /,  consists  of  a  solenoid,  7, 
whose  armature  or  core  carries  an  indicating  banner,  F,  to 
which  is  pivoted  a  lever,  G,  provided  with  a  knob.  /  is  in  series 
with  the  contacts  closed  by  movement  of  (?,  hence  when  the 
latter  is  in  its  lower  position,  current  cannot  pass  through  the 
circuit  of  the  line  battery,  B. 


FIG.  76 


When  G  is  raised,  the  circuit  is  completed  at  /,  and  if  the 
circuit  controller,  A,  is  closed,  a  current  will  pass  around  /,  and, 
the  core  being  energized,  will  maintain  this  condition  until  A  is 
open-circuited.  When  this  current  flows,  D  is  thrown  to  the 
clear  position  by  current  from  the  local  battery,  C.  A}  there- 
fore, must  be  closed  (by  movement  of  the  home  signal)  before 
G  is  moved;  should  this  sequence  of  events  not  occur,  D  cannot 
be  cleared.  Since  A  is  closed  by  the  action  which  clears  H,  it 
is  evidently  impossible  for  an  approaching  train  to  pass  D,  with- 
out receiving  a  cautionary  signal,  unless  a  clear  condition  at 
the  cabin  obtains. 

Somewhat  similar  to  the  above  in  the  arrangement  of  acces- 
sories and  circuits,  is  that  shown  in  Fig.  77.  In  addition,  a 
circuit  controller,  P,  having  a  positive  connection  to  the  home 


72 


AUTOMATIC  BLOCK  SIGNALS 


signal  lever,  B,  is  included.  When  B  is  thrown  in  the  direction 
of  the  arrow,  H  is  moved  to  the  clear  position,  and  the  contacts 
at  P  closed.  Unless  the  armature  of  the  indicator,  A,  is  raised, 
however,  E  will  not  receive  current  from  the  line  battery,  C, 


FIG.  77 

hence  D  cannot  be  cleared.  The  banner  on  the  indicator  may 
be  in  the  form  of  a  miniature  semaphore,  or  a  small  banner  which 
appears  before  a  glass-covered  aperture  in  the  case. 

Adding  a  circuit  controller,  (7,  to  the  above,  the  arrangement 
produced  in  Fig.  78  is  evident.    This  comprehends,  as  above 


•  FIG.  78 

stated,  the  addition  of  a  protective  or  interlocking  function,  the 
principle  of  the  working  circuits  being  unchanged. 

An  indicator  and  magnetic  circuit  controller  may  have  its 
movements  automatically  governed  by  the  use  of  a  setting  track 
section,  in  which  the  movement  of  a  train  sets  up  conditions 
that  actuate  this  mechanism.  In  Fig.  79,  D  is  a  short  setting 
section  having  the  battery,  (?,  and  the  track  relay,  F.  This 


SEMI-AUTOMATIC  CIRCUITS 


73 


section  may  be  of  any  required  length,  but  as  only  a  momentary 
initial  current  is  required  for  setting  this  function,  it  usually  is 
of  but  several  rail  lengths. 

If  the  section,  D,  is  occupied,  the  circuit  controller,  A,  and  the 
indicator,  (7,  have  no  control  over  E.  But  should  it  not  be  occu- 
pied, then,  if  the  operator  raises  the  armature  of  C,  with  H  at 


FIG.  79 


the  clear  position,  E  will  raise  its  armature,  thus  sending  current 
from  K  to  D  and  clearing  the  latter. 

Extension  of  the  above  principle  produces  the  circuit  diagram 
given  in  Fig.  80.  The  lever  E  at  the  block  tower  is  for  the 
express  purpose  of  operating  the  controller  with  which  it  is 
associated.  When  the  home  signal,  H,  is  cleared,  the  contacts 
at  G  will  be  closed.  E  is  then  thrown  in  the  direction  of  the 


FIG.  80 


arrow,  which  will  cause  a  current  to  flow  from  N  through  F 
and  B,  if  the  setting  section,  0,  is  unoccupied.  Should  a  train 
be  in  this  section,  however,  A  will  be  deenergized,  and,  by  its 
armature's  falling,  open-circuit  N,  thus  depriving  F  and  B  of 
current,  and  preventing  D  from  being  cleared  by  C.  If  the 
armature  of  F  be  restored,  the  same  condition  will  obtain,  since 
the  circuit  is  still  open  at  the  armature  of  A. 


74  AUTOMATIC  BLOCK  SIGNALS 

The  circuits  at  a  representative  mechanical  interlocking  tower, 
16,  are  shown  in  Fig.  81.  15  is  a  charging  plant  from  which 
power  lines  run  to  the  various  storage  batteries.  At  the  east- 
bound  signal,  6,  the  track  polarity  is  under  the  control  of  the 
arrangement,  4,  the  operating  magnet  being  in  series  with  the 
contacts,  5  (closed  when  6  is  clear),  two  of  the  controller  con- 
tacts, 10,  battery  8,  and  the  cable.  Signal  6  is  operated  by 
battery  18,  through  line  23  and  armature  of  25,  and  signal  1 
(at  clear)  by  battery  3,  through  the  polar  contacts  of  the 
polarized  relay,  2.  The  latter  receives  current  from  a  track  cell 
and  reverser  in  the  rear,  while  24  energizes  20.  Relay  21  operates 
a  reverser  connected  to  a  section  preceding  14,  the  latter  receiving 
current  from  3  through  the  interlocking  tower. 

A  circuit  controller,  17,  is  opened  when  the  signal,  26,  is  at 
danger,  and  is  in  series  with  the  next  signal  in  the  rear.  A 
track  relay,  22,  is  connected  to  the  crossing  track,  27,  its  armature 
contact  being  in  series  with  the  front  contacts  of  20  and  28. 
The  series  electric  locks,  7,  applied  to  mechanical  levers,  are 
connected  to  battery  8  through  lines  29  and  31  and  common 
line  30.  Controller  13,  operated  by  14,  is  in  series  with  con- 
trollers 10,  contacts  5,  relay  4,  and  21.  Considering  the  circuits 
already  described,  no  difficulty  should  be  encountered  in  com- 
prehending the  entire  arrangement.  It  is  evident  in  the  above 
circuit  diagrams  that  a  common  main  battery  may  be  used  for 
numerous  functions.  In  practice  a  single  battery  is  often  em- 
ployed to  furnish  current  for  a  multiplicity  of  such  receptive 
devices,  and  sometimes  to  energize  an  entire  circuit  network 
of  great  complexity. 

The  normal  clear  circuits  at  the  Newark  drawbridge  of  the 
D.  L.  &  W.  over  the  Passaic  River  are  shown  in  Figs.  82  to  87. 
The  plans  are  consecutive  from  A  to  J,  lines  and  other  circuit 
wires  being  numbered  to  render  easy  tracing  up  possible.  No.  7 
is  the  common  line  and  its  connections,  and  is  shown  heavy. 

In  Fig.  82  signals  M  81  are  for  west-bound  movements,  and 
M  82  for  east  bound,  all  four  being  placed  upon  a  signal  bridge. 
Relays  marked  NP  are  both  neutral  and  polarized,  while  those 
marked  H  are  neutral  only,  and  have  resistances  of  four  ohms. 
The  distant  blades  at  M  82  are  semi-automatic,  40  being  con- 
trolled by  the  armature  contacts  of  the  500-ohm  slow  releasing 
relay  42,  through  the  circuit  breaker,  43  (operated  by  the  home 


SEMI-AUTOMATIC  CIRCUITS 


75 


76 


AUTOMATIC  BLOCK  SIGNALS 


blade),  the  line  28,  and  east-bound  hand  switch,  E,  at  the  me- 
chanical interlocking  tower  of  Fig.  84.  The  home  blade,  44, 
operates  two  circuit  breakers,  45  and  46,  they  being  connected 
in  series  with  the  distant  and  line  32,  the  latter  passing  to  the 
middle  east-bound  distant  at  the  next  bridge  west.  Line  No.  35 


-A/- 


FIG.  82 

passes  to  the  west-bound  middle  track  distant  indicator  for 
Roseville  Avenue,  No.  26  to  the  east-bound  distant  indicator, 
No.  31  to  the  west-bound  (outside  track)  distant  indicator  for 
Roseville  Avenue,  No.  30  to  the  operating  mechanism  of  the 
middle  east-bound  home  signal  at  the  next  bridge  west,  No.  32 
in  series  with  the  operating  devices  at  the  distant  of  the  same 
signal,  and  ^.-50  to  the  transmitter,  T,  at  Fig.  84. 


SEMI-AUTOMATIC  CIRCUITS 


77 


The  500-ohm  slow  releasing  relay  47  is  energized  through 
lines  29,  the  circuit  breaker  49  at  mechanical  signal  16  of  Fig. 
83,  the  middle  east-bound  hand  switch,  M.E.,  at  E-F,  and  bat- 
teries 50;  returning  through  the  common,  to  which  all  working 
batteries  and  most  of  the  other  accessories  have  one  side  con- 
nected. Its  armatures  are  in  series  with  41  through  45.  Relay 
48  is  controlled  from  the  armature  of  51  at  C-D  through  line 
27,  and  controls,  through  its  armature,  both  41  and  44.  The 
signal  batteries  52-53-54-55  operate  the  signal  mechanisms 


FIG.  83 

they  are  adjacent  to,  the  polarity  reversers  being  operated  by 
the  home  blades  of  these  signals. 

In  Fig.  83  the  west-bound  signals,  M  77,  are  purely  automatic, 
and  controlled  by  the  polarized  track-relay  56;  while  15  and  16 
are  semi-automatic,  and  under  the  control  of  electric  slots  in 
series  with  lines  18  and  20.  Relays  57  and  62  are  in  multiple, 
and  connected  to  common  and  line  2,  in  series  with  the  lower 
armature  or  front  contact  of  east-bound  track-relay  64.  Line  2 
runs  to  the  circuit  breaker  82  of  1  D  at  E-  F,  and  the  track-relay 
contact  86  at  this  point;  the  slow  releasing  relay  57  controlling 


78  AUTOMATIC  BLOCK  SIGNALS 

the  distant  arm  58  through  the  circuit  breaker  67;  60  and  66 
being  thrown  by  levers;  59  is  controlled  by  62,  and  is  clear  when- 
ever 58  is,  since  62  and  57  are  in  multiple. 

At  63  a  switch  merges  the  east-bound  and  middle  tracks, 
thus  removing  the  necessity  for  four-movement  indication.  68 
is  the  independent  local  battery  for  58,  and  69  for  59.  Neutral 
track  relays,  100  and  119,  produce  the  required  track  circuit 
and  line-wire  control.  Although  it  is  possible  to  use  a  smaller 
number  of  batteries,  line  wires,  relays,  etc.,  in  such  a  com- 
plicated situation  and  produce  the  same  results,  crossing  of 
circuit  wires  would  set  up  conditions  that  would  entail  con- 
siderable vexation  in  eradicating,  while,  by  the  use  of  as  many 
independent  circuits  as  is  consistent  with  economy,  such  troubles 
seldom  occur,  and  are  more  readily  traced.  The  use  of  common 
wires  has  often  led  to  troublesome  conditions,  but  such  is 
usually  the  result  of  poor  insulation  and  careless  installation 
or  maintenance. 

In  Fig.  84  the  circuits  at  the  mechanical  interlocking  tower 
are  given.  E,  M.E.,  W,  and  M.W.  are  the  east,  middle  east, 
west,  and  middle  west-bound  control  line  switches.  One  side 
of  each  of  the  east  switches  is  connected  to  the  common  battery 
wire,  By  and  the  multiple  batteries  at  50,  the  other  sides  being 
connected  to  lines  28  and  29,  in  series  with  circuit  breakers  49 
and  70,  and  through  additional  circuits  already  traced.  An 
intercommunicating  telephone  instrument,  71,  is  in  circuit  with 
72  at  the  drawbridge  (G-H)  so  that  communication  can  be 
carried  on  between  these  points.  73  to  79  are  indicators,  73, 
74,  75,  and  79  having  contact  armatures,  the  energization  of  the 
magnets  thus  clearing  not  only  their  banners  but  raising  also 
these  armatures.  A  sixty-ohm  bell,  80,  is  closed  by  a  back 
contact  of  either  73  or  74,  81  being  energized  through  the  back 
contact  on  79. 

73  receives  current  from  battery  54,  through  line  25,  and 
the  front  neutral  contact  of  polarized  track  relay  98  at  A-B, 
and  is  the  middle  east-bound  indicator;  75  is  the  east-bound 
home  through  battery  50,  line  24,  contact  of  relay  64,  and  com- 
mon; 76  the  east-bound  advance  by  way  of  line  22,  contact 
of  86,  and  common;  77  the  middle  home  through  line  23  front 
contact  of  100,  and  common;  78  the  west-bound  home  by  line 
21,  front  contact  of  90,  and  common;  79  the  west-bound  distant 


SEMI-AUTOMATIC  CIRCUITS 


79 


80  AUTOMATIC  BLOCK  SIGNALS 

by  line  15,  contact  15,  cable,  west-bound  home  indicator  contact 
of  101,  to  battery  by  the  front  contact  of  106. 

82  is  the  lock  magnet  on  mechanical  lever  No.  16,  which 
operates  the  home  semaphore,  16,  at  C-D,  and  is  energized 
from  50  through  the  front  contacts  of  73  and  74  in  multiple; 
that  is,  it  releases  the  lever  whenever  either  its  east-bound 
middle  or  east-bound  distant  is  cleared;  83  is  the  lock  for  lever  15, 
or  east-bound  outside  semaphore  at  C-D;  84  for  No.  6  at  116; 
and  85  for  No.  5  at  116.  Unless  90  is  energized  the  semaphores 
at  117  will  be  in  the  stop  position,  because  of  the  slots,  89  and 
116,  which  are  thus  controlled  by  a  track  circuit.  Circuit 
breaker  115  is  in  series  with  line  3  and  one  front  contact  of  90, 
also  one  contact  of  119,  circuit  breaker  at  M-77,  battery  120 
and  common,  and  on  the  other  side  through  line  3,  and  con- 
nector 3  at  88,  and  cable.  117  is  in  series  with  one  of  the  front 
contacts  of  90,  line  5,  5  at  88,  cable,  circuit  breaker  126  at  7J, 
500-ohm  relay  130,  and  common.  A  slot,  97,  also  controls  1  D 
(at  which  a  derail  appears)  through  86,  line  16  and  battery  B. 
Subsidiary  devices  do  not  enter  in  this  case,  as  the  track  circuit  at 
the  approach  and  over  the  draw  perform  all  the  necessary  func- 
tions. The  cable  is  carried  to  the  center  of  the  draw,  the  track 
circuit  connections  being  made  so  that  the  track  forming  part 
of  the  draw  is  electrically  continuous  with  that  at  the  abut- 
ments. The  circuit  breaker,  82,  is  in  series  with  line  2,  front 
contact  of  86,  common,  2  at  64,  east-bound  hand-control  switch 
113,  connector  2,  cable,  circuit  breaker  122  at  M-74  (/-«/), 
battery  121,  and  common.  At  127  there  is  a  derail,  as  also  at 
129. 

Continuing  on  Fig.  85  (G-H),  the  bridge  controller  lock,  112, 
is  in  series  with  a  circuit  breaker  on  lever  No.  5,  which  is  open 
when  the  bridge  is  locked,  so  that  when  the  former  is  energized, 
the  bridge  is  not  in  its  safe  position.  A  single-stroke  bell,  107, 
is  connected  to  the  armature  contact  of  approach  indicator  105, 
so  that  when  the  latter  has  a  current  passed  through  its  coils, 
the  gong  will  be  struck  once,  this  occurring  through  line  37, 
whose  connections  will  be  shown  later.  109  receives  battery 
current  through  the  back  contact  of  the  west-bound  distant  indi- 
cator, 106,  and  108  through  the  same  contact  of  the  east-bound 
distant  indicator,  102.  The  bridge  indicator,  104,  is  in  series  with 
the  wire  36  and  the  signal  battery  at  9  D,  through  the  cables; 


SEMI-AUTOMATIC  CIRCUITS 


81 


103  is  the  east-bound  home  indicator  connected  to  battery  50 
and  line  4;  the  circuit  being  completed  through  one  of  the  front 
contacts  of  86  and  common.  The  lock  magnet,  111,  is  connected 


H 


FIG.  85 

to  lever  9  of  that  signal,  and  is  in  series  with  the  front  contact  of 
106.  The  west-bound  distant  indicator  106  is  connected  by  line 
1  to  the  cable,  one  contact  armature  of  135,  and  to  the  west- 


82 


AUTOMATIC  BLOCK  SIGNALS 


bound  home  indicator  at  Harrison,  the  next  signal  point 
east  line  11  E,  operating  the  west-bound  distant  signal  at 
this  point. 

In  Fig.  86  (I-J)  the   east  end  of  the  cable  and  connections 


are  shown  with  the  mechanical  semaphore,  9  D,  and  the  automatic 
signals,  Af-74  and  Af-69.  The  four-ohm  track  relay,  135,  con- 
trols east-bound  signal  lf-69,  137  being  the  working  battery. 
A  high-resistance  slow-releasing  magnet,  136,  is  in  series  with  line 


SEMI-AUTOMATIC  CIRCUITS 


83 


33,  circuit  breaker  124,  cable,  west  hand-switch  114,  and  battery 
145;  while  a  similar  magnet  130  is  in  series  with  the  circuit 
breaker,  126,  and  line  5  (all  three  circuit  breakers  are  closed 
when  9  D  is  cleared).  9  D  is  also  under  the  control  of  slot  128, 
which  is  energized  through  the  track  relay  contacts.  Circuit 
breaker  125  controls  140,  and  138  the  preceding  distant  sema- 


t  Sig  9O 


FIG.  87 

phore,  while  139  is  in  series  with  the  distant  at  lf-69.  A  polar- 
ized relay,  141,  is  used  at  Af-74,  battery  121  operating  both  home 
and  distant  semaphores. 

The  track  circuit  and  other  connections  at  the  lower  deck  of 
the  draw  appear  in  Fig.  87,  with  two  manual  signals,  9  D  and 
10  D.  With  the  foregoing  description  in  view,  it  need  not  be 
dissected. 


CHAPTER   VI. 
BATTERIES. 

THE  primary  cells  most  generally  used  in  signal  installations 
are  the  following:  (1)  Gravity;  (2)  Gordon;  (3)  Edison.  All 
are  of  the  closed-circuit  type;  that  is,  they  are  capable  of 
withstanding  continuous  full  normal-current  discharge. 

Open-circuit  cells  are  but  little  used;  for,  while  certain  work 
is  intermittent  in  character,  it  has  been  found  that  cells  of  this 
type  are  not  to  be  depended  upon.  For  ringing  electric  bells  at 
places  where  inoperation  will  not  result  in  serious  consequences, 
the  Leclanche  or  sal-ammoniac  cell  has  been  applied  with  re- 
strictions. 

In  the  gravity  cell,  which  is  of  the  two-fluid  type,  the  different 
specific  gravities  of  the  liquids  used  is  the  only  principle  involved 
in  keeping  them  apart;  porous  cups  and  diaphragms  being 
thereby  eliminated.  These  liquids  are  a  saturated  solution  of 
copper  sulphate  and  a  dilute  solution  of  zinc  sulphate  and  sul- 
phuric acid,  the  latter  being  formed  only  during  the  action  of 
the  cell,  which  is  shown  in  Fig.  88.  The  copper  element,  C, 
rests  upon  the  bottom  of  the  containing  jar,  and  is  connected  to 
the  external  circuit  by  an  insulated  wire.  The  copper  is  partly 
covered  with  crystals  of  blue  stone  or  copper  sulphate  (CuSO), 
these  crystals  being  surrounded  by  a  strong  solution  of  copper 
sulphate.  Above  this  latter  solution,  and  distinctly  separate 
from  it,  is  the  solution  of  zinc  sulphate,  in  which  the  zinc,  Z  (a 
common  type  of  which  is  shown  also  at  D),  is  immersed.  This 
zinc  is  supported  by  the  bent  bare  copper  wires,  G,  which  are 
cast  in  the  former.  The  action  of  the  cell  is  as  follows : 

When  the  external  circuit  is  closed,  the  small  amount  of 
sulphuric  acid  (or  water  if  the  former  is  not  present)  attacks  the 
zinc,  forming  zinc  sulphate  and  hydrogen.  The  zinc  sulphate 
remains  in  the  upper  part  of  the  liquid,  while  the  hydrogen 
passes  to  the  copper  sulphate,  and  thus  forms  sulphuric  acid 

84 


BATTERIES 


85 


and  metallic  copper.    The  copper  is  deposited  upon  the  copper 
element,  while  the  sulphuric  acid  rises  and  attacks  the  zinc, 
this  cycle  being  repeated  as  long  as  the  external  circuit  is  closed. 
These  reactions  are  expressed  as  follows :  — 

Zn  +  H2S04  =  ZnS04  +  2H. 
2H  +  CuS04  =  H2S04  +  Cu. 

When  the  water  of  the  solution  is  decomposed,  oxygen  is  liberated. 
The  copper  which  is  deposited  upon  the  copper  element  must  be 
loosened  each  time  the  cell  is  renewed,  or  the  accumulations 


FIG.  88 

will  become  too  solid  for  removal.  When  a  gravity  cell  is  in 
proper  condition,  the  blue  line  of  separation  should  be  midway 
between  the  two  electrodes. 

The  e.m.f.  of  this  cell  on  open  circuit  is  1.07  volts;  and  the 
internal  resistance  from  about  .5  to  3  ohms.  This  will  give  a 
current  on  short  circuit  of  from  .3  to  2.5  amperes.  The  cell  is 
most  commonly  used  for  track  circuits  on  account  of  its  perfect 
electrochemical  depolarization.  To  a  certain  limit  of  saturation 
of  the  upper  or  zinc  sulphate  solution,  the  greater  the  con- 
tinued demand  the  more  satisfactory  the  operation.  A  disad- 
vantage of  the  cell,  however,  is  the  high  internal  resistance. 


86  BATTERIES 

The  loss  this  entails  depends  upon  the  resistance  of  the  circuit 
to  which  it  is  connected;  since  this  loss  (C2R)  depends  upon  the 
relation  of  the  internal  resistance  to  the  total  resistance. 
The  internal  resistance  of  a  gravity  cell  being  0.5  ohm,  the 

c2 
maximum  -  factor  that  can  safely  be  allowed  is  2,  which  at  .30 

gives  an  economic  power  valuation  of  2.2. 

In  the  Gordon  cell,  the  elements  are  iron  and  zinc,  while  the 
exciting  liquid  is  a  strong  solution  of  sodium  hydrate  or  caustic 
soda,  NaOH.  The  containing  jar  is  either  glass,  porcelain,  or 
enameled  steel,  depending  upon  the  conditions  to  be  met. 
Steel  and  porcelain  have  a  longer  life,  and  are  much  less  liable 
to  failure  during  recharging  and  operation  than  glass,  but  the 
operation  of  the  cell  is  not  visible,  as  is  desirable  to  determine 
the  point  when  renewal  must  be  accomplished. 

Fig.  89  illustrates  a  300-ampere-hour  cell,  such  as  is  most 
frequently  used  for  signal  and  grade-crossing  circuits,  the  jar 
being  6  in.  by  8  in.  in  size.  Z  is  the 
positive  zinc  element,  which  is  a  sheet 
bent  to  a  cylindrical  form;  it  being  of 
about  one-eighth  of  an  inch  in  thickness. 
This  is  thoroughly  amalgamated,  to  pre- 
vent local  action,  and  is  supported  on 
three  porcelain  lugs,  P,  fastened  to  the 
perforated  cylinder,  D,  which  it  sur- 
rounds. This  latter  is  partly  filled  with 
a  flaky  oxide  of  copper  (CuO),  the  iron 
and  this  compound  forming  the  negative 
element.  Contact  is  made  to  Z)  by  a 
binding  post  or  connector,  the  threaded 
connection  to  which  is  screwed  into  a 
nut  in  the  top  of  the  cylinder.  The  sheet  iron  cover,  C,  supports 
D  and  Z  by  the  binding  action  of  two  porcelain  washers,  A,  one 
above  and  the  other  below  C.  The  zinc  is  connected  to  the 
external  circuit  by  the  insulated  wire,  W,  which  is  riveted  to 
the  former  and  further  insulated  from  C  by  a  small  porcelain 
bushing.  The  riveted  connection  is  covered  with  asphaltum 
to  prevent  local  action  at  the  junction  of  the  copper  and  zinc. 
When  the  cell  is  renewed,  the  entire  cylinder  and  contents, 
also  the  remaining  zinc,  is  thrown  in  a  scrap  pile.  Formerly, 


BATTERIES  87 

the  exhausted  copper  oxide  was  removed  and  replaced,  the 
entire  arrangement  being  dismantled  to  do  this;  resulting  in 
much  labor  and,  without  care,  painful  sores  on  the  hands  of  the 
battery  man.  Thus  one  of  the  objectionable  features  of  the 
sodium  hydrate  cell  has  been  removed. 

An  exciting  solution  of  from  20  to  25  per  cent  is  employed; 
in  other  words,  three  or  four  pounds  of  water  to  one  pound  of 
pure  caustic  soda.  The  copper  oxide  and  zinc  are  so  propor- 
tioned that  all  the  elements  are  exhausted  at  once.  A  heavy 
mineral  oil  is  used  to  cover  the  surface  of  the  exciting  solution, 
as  this  latter  has  a  strong  affinity  for  the  C02  of  the  atmosphere, 
which  if  not  otherwise  prevented  would  result  in  rapid  deterio- 
ration of  the  cell.  The  reaction  is  shown  in  the  formula: 

2NaOH  +  C02  =  Na2C03  +  H20. 

The  sodium  carbonate  (Na2C03)  thus  formed  is  not  only  of 
little  value  in  setting  up  an  e.m.f.,  but  it  also  is  of  a  creeping 
character,  crystalization  taking  place  over  the  edges  of  the  jar 
and  cover,  resulting  in  rapid  destruction  of  the  latter. 

During  the  action  of  the  cell,  sodium  zin'cate  is  formed  as 
follows : 

2NaOH  +  Zn  =  Na2Zn02  +  2H2. 

The  hydrogen  passes  to  the  copper  oxide  and  forms  water 
and  metallic  copper,  thus: 

2H  +  CuO  =  Cu  +  H,0. 


The  Edison  cell  is  also  of  the  single-fluid  type,  and  now  em- 
ploys an  exciting  solution  of  caustic  soda  or  sodium  hydrate, 
NaOH.  In  its  action  it  is  somewhat  similar  to  the  Gordon,  but 
of  a  different  mechanical  construction.  Formerly,  caustic  pot- 
ash solution  was  used,  but  as  this  is  even  more  difficult  to  handle 
than  the  sodium  compound,  it  has  been  abandoned.  Fig.  90 
shows  the  cell  in  part  section.  A  cover,  B,  of  porcelain,  has  a 
recess  which  fits  into  the  top  of  the  containing  jar.  In  the 
center  of  this  cover  there  is  a  boss,  on  each  side  of  which  stems 
or  lugs,  L,  incorporated  with  the  zinc  plates,  Z,  are  securely 
clamped  by  the  thumbscrew  connector,  C.  Within  a  slotted 
frame  of  copper,  F,  are  placed  two  porous,  compressed,  and 
beveled  plates  of  cupric  oxide,  0,  with  surfaces  reduced  to  the 


88 


AUTOMATIC  BLOCK  SIGNALS 


B 


-L, 


FIG.  90 


metallic  state  for  increased  conductivity.  These  plates  have 
a  binder  of  magnesic  chloride,  and  are  secured  in  place  by  the 
copper  thumb  bolts,  N.  Two  insulating  tubes  of  hard  rubber, 

T,  are  placed  on  part  of  the  frame 
which  emerges  from  the  liquid,  and 
prevent  the  current  from  leaking 
across  the  surface  of  the  liquid  to 
parts  of  opposite  polarity,  also  pro- 
tecting the  frame  from  corrosion  at 
the  junction  of  the  oil  and  solution. 
The  liquid  is  covered  as  before  with  a 
heavy  mineral  oil,  and  the  external 
circuit  wires  are  fastened  to  the  con- 
nectors, A  and  C. 

The  cell  is  renewed  by  removing 
the  zincs,  oxide  plates,  and  solution, 
and  replacing  by  new  elements,  care 
being  taken  to  have  all  nuts  and 
connections  tight.  The  entire  old 
solution  is  thrown  away  and  the  new  liquid  substituted,  a 
fresh  bottle  of  oil  being  poured  over  the  surface.  Before 
replacing  the  new  elements,  they  should  be  dipped  in  clean 
water,  to  prevent  the  oil,  which  is  of  high  viscosity,  from 
adhering  when  they  are  immersed  in  the  solution. 

The  water  used  in  renewing  all  cells  should  be  taken  from  a 
running  stream  or  hydrant,  as  stagnant  water  contains  vege- 
table and  animal  impurities  which  render  it  unfit  for  battery 
purposes.  For  this  reason  it  is  not  practicable  to  locate  barrels 
filled  with  water  near  the  battery  chutes,  as  animalculse  soon 
manifest  themselves.  Spring  water,  is  not  always  valuable,  as 
it  may  contain  mineral  substances  whose  reaction  is  deleterious 
to  the  proper  action  of  the  cell.  When  mixing  caustic  soda 
solution,  the  soda  should  be  slowly  poured  into  the  water,  and 
the  latter  rapidly  stirred  at  the  same  time,  as  failure  to  do  this 
will  result  in  its  falling  to  the  bottom  and  solidifying.  Should 
any  of  the  solution  get  on  the  hands  or  face  it  may  be  readily 
eliminated  by  applying  a  vegetable  or  animal  oil  or  grease, 
which  is  thus  converted  into  soap.  If  glass  jars  are  used,  they 
should  be  placed  on  dry  wood  or  ties,  to  prevent  cracking  at 
the  bottom,  owing  to  unequal  expansion. 


BATTERIES  89 

The  surface  of  the  liquid  should  be  about  one  inch  above  the 
top  of  the  zinc  and  oxide  plates,  for  if  the  latter  project  above 
the  liquid,  the  bare  parts  will  be  rapidly  destroyed.  Also  fine 
particles  of  metallic  copper  may  fall  from  the  oxide  plates  and 
by  floating  upon  the  plane  of  separation  of  the  oil  and  solution, 
ultimately  short-circuit  the  cell.  The  condition  of  the  oxide 
plates  may  be  ascertained  by  picking  into  them  with  a  sharp 
knife.  Should  they  be  copper  colored  throughout,  they  are 
exhausted;  but  if  the  central  portion  is  black,  they  are  still  of 
use,  the  continuity  of  life  depending  upon  the  relative  thickness 
of  this  inner  black  layer.  Using  an  exhausted  set  of  plates 
results  in  rapid  depolarization,  while  it  is  not  advisable  to  use 
plates  that  have  been  left  in  the  air  and  consequently  partially 
reoxidized,  as  this  natural  oxidization  occurs  only  superficially. 

A  300-ampere-hour  capacity  has  an  internal  resistance  of 
.025  ohm,  a  working  voltage  of  .667,  a  continuous-current  de- 
livery of  6  amperes,  a  short-circuit  current  of  26.7  amperes; 

c2  c2 

consequently  a  —  factor  of  17.78,  and  a  —  factor  of  5.34,  when 
v  pr 

p  =  .30.  The  low  internal  resistance  is  advantageous  when 
the  cell  is  called  upon  to  deliver  heavy  currents;  that  is,  when 
connected  to  a  low  external  resistance.  The  ratio  of  the  energy 
lost  in  the  cell  to  the  total  energy  expended  is  then  very  low. 

The  disadvantages  of  the  sodium  hydrate  cells  are  the  caustic 
nature  of  the  exciting  liquid,  the  low  terminal  voltage,  the 
rapidity  with  which  they  give  out,  and  the  excessive  heat  caused 
by  the  dissolving  of  caustic  soda  in  water.  The  indication  that 
a  cell  needs  renewing  is  the  segregation  of  crystals  of  sodium 
zincate  upon  the  zinc  element,  a  condition  occurring  without 
much  warning.  The  use  of  oil  on  the  surface  of  a  liquid  is  also 
rather  troublesome,  as  the  inside  surface  of  the  jars  must  be 
frequently  cleaned.  Also  a  large  percentage  of  the  cost  of 
operation  is  in  scrap  which  is  not  really  utilized. 

The  advantages  are  the  uniformity  of  operation,  freedom 
from  local  action,  low  internal  resistance,  constancy  of  current 
output,  ability  to  withstand  low  temperatures,  the  absence  of 
noxious  or  combustible  vapors,  and  the  adaptability  for  heavy 
current  output. 

Storage  cells  have  many  advantages  over  primary  cells  which 
make  them  particularly  adaptable  to  certain  phases  of  signaling. 


90  AUTOMATIC  BLOCK  SIGNALS 

Where  large  amounts  of  energy  are  required,  and  it  is  not  advis- 
able to  install  a  separate  generating  plant,  storage  cells  may  be 
economically  applied,  being  charged  by  a  portable  generating 
set.  Such  an  arrangement  has  the  advantage  of  a  large  and 
steady  output,  with  a  smaller  number  of  cells  than  the  closed- 
circuit  primary  cells  we  have  considered  can  have.  The  average 
e.m.f.  of  a  storage  cell  is  2  volts,  so  that  three  Edison  cells  can 
be  replaced  by  one  storage  cell,  as  far  as  voltage  is  concerned. 
When  a  stationary  generating  set  is  used,  the  signal  batteries  are 
charged  through  the  aid  of  line  wires  which  run  from  the  plant 
and  include  the  cells  in  series. 

Most  of  the  accumulators  used  in  signal  practice  have  positive 
and  negative  plates  of  lead  and  an  electrolyte  of  dilute  sulphuric 
acid  (four  parts  of  water  by  volume  to  one  part  of  acid,  giving 
a  specific  gravity  of  1.2).  The  lead  plates  are  "  formed  " 
mechanically  or  electrically,  and  are  fastened  together  in  sub- 
stantial shape. 

Storage  cells  are  rated  according  to  the  number  of  ampere- 
hours  they  are  capable  of  discharging  until  the  terminal  e.m.f. 
of  a  cell  falls  to  1.8  volts,  the  e.m.f.  when  fully  charged  being 
2  volts.  However,  since  sulphating  sets  in  below  1.9  volts,  they 
should  never  be  discharged  until  the  e.m.f.  becomes  less  than 
this  figure. 

A  300-ampere-hour  cell  may  be  charged  at  a  normal  current 
of  30  amperes,  the  charging  continuing  for  10  hours;  which 
also  represents  the  normal  rate  of  discharge.  Smaller  capacities 
require  less  current;  a  50-ampere-hour  cell  taking  5  amperes 
under  normal  conditions.  It  is  better  practice  to  prolong  the 
charging  time  by  decreasing  the  current.  Better  results  are 
also  obtained  when  discharging  at  a  low  rate,  a  150-ampere-hour 
cell  being  capable  of  delivering  190  ampere-hours  with  38  hours 
allowed  for  both  charge  and  discharge,  and  only  120  ampere- 
hours  at  5  hour  discharge  rate. 

When  charging,  the  e.m.f.  of  the  generator  should  be  10  per 
cent  greater  than  the  total  e.m.f.  of  the  cells  when  charged. 
The  resistance  of  a  cell  is  very  low  (.003  ohm  for  an  average  300 
ampere-hour  cell),  hence  it  is  necessary  to  include  a  resistance 
of  some  kind  in  series  when  charging.  To  illustrate,  suppose  40 
such  cells  were  connected  in  series  on  a  110-volt  circuit.  The 
cell  e.m.f.  which  will  oppose  that  of  the  supply  circuit  would  be 


BATTERIES  91 

40  X  1.9,  or  76  volts.  Then  110  —  76  =  34  volts;  resulting  in 
a  flow  of  34  -^  (40  X  .003)  =  283.3  amperes,  which  of  course 
is  an  excessive  current.  With  a  resistance  of  one  ohm  in  series, 
on  the  other  hand,  the  current  would  be  34  H-  1.12,  or  30.3 
amperes,  which  is  a  normal  value. 

Usually  the  line  has  sufficient  resistance  to  prevent  an  excessive 
current  flow;  but  jn  any  event  it  requires  careful  calculation. 
It  is  advantageous  to  have  a  small  variable  resistance  (rheostat) 
in  circuit  so  that  the  charging  current  may  be  adjusted  to  the 
required  value. 

Accumulators  should  be  installed  in  a  dry  place,  having 
an  average  temperature  of  about  70°  F.  Charging  may  be 
continued  until  gasing  sets  in,  a  phenomenon  caused  by  the 
liberation  of  hydrogen,  which  gives  the  electrolyte  a  boiling 
appearance.  High  insulation  must  be  maintained;  otherwise 
the  leakage  factor  will  be  high,  and  trouble  encountered  with 
foreign  currents  in  the  track  circuits. 

Storage  batteries  may  be  charged  from  commercial  power 
circuits,  or  through  the  medium  of  a  portable  generating  plant. 
In  the  latter  case,  gasoline  engines  are  preferable,  the  generator 
being  direct  driven,  except  in  the  case  of  small  units.  If  alter- 
nating current  is  available,  it  is  converted  to  direct  at  the  proper 
voltage  by  a  motor  generator  or  mercury  rectifier.  In  all- 
electric  interlocking  110  volts  is  the  standard  pressure;  55 
storage  cells  being  connected  in  series  to  obtain  this  e.m.f.  The 
capacity  of  the  individual  cells  depends  upon  the  work  they 
perform  in  a  given  time,  usually  24  hours,  the  cells  being 
charged  so  often.  With  such  installations,  a  switchboard  is 
necessary.  Such  a  board  should  contain  an  ammeter,  volt- 
meter, pilot  lamps  for  indicating  grounds,  circuit  switches, 
charging  rheostat,  fuses,  and  circuit  breakers  (both  overload 
and  reverse  current). 

A  mercury  converter  or  rectifier  is  now  used  for  charging 
storage  signal-batteries  from  alternating-current  mains.  This 
device  suppresses  the  negative  wave  of  the  alternating  side  and 
converts  it  into  a  pulsating  direct  current,  with  intervals  of  par- 
tial current  cessation.  Such  a  current  can  readily  be  employed 
for  charging  purposes,  although  it  could  not  be  used  directly  on 
the  signal  motors  or  relays,  due  to  the  resistance  offered  by 
such  inductive  devices;  with  consequent  heating  and  loss  of 


92 


AUTOMATIC  BLOCK  SIGNALS 


BATTERIES 


93 


energy  from  eddy  currents  and  inconstancy  of  the  available 
e.m.f. 

Mercury  rectifiers  should  be  mounted  upon  a  switchboard, 
containing  the  main  switches  and  connections,  with  a  trans- 
former, having  a  variable  secondary  voltage.  The  charging 
wires  run  either  to  separate  portable  battery  sets,  or  to  the 
charging  line.  This  arrangement  is  not  only  economical,  but 


FIG.  92 

practicable;  and  transmission  may  be  effected  over  great  dis- 
tances, and  from  isolated  points,  at  any  primary  potential. 

Fig.  91  is  the  plan  of  a  charging  arrangement  used  on  the 
D.  L.  &  W.  is  shown.  The  charging  plant  is  located  at  Hal- 
stead,  N.  Y.  (192.5  miles  from  New  York  City),  the  total 
territory  covered  being  17.7  miles.  Forty-four  two-arm  signal 
mains  are  charged  in  this  fashion;  A,  B,  and  G  being  slotted 
mechanical  signals. 

While  nearly  all  forms  of  primary  batteries  used  in  signal 


94  AUTOMATIC  BLOCK  SIGNALS 

practice  are  of  the  non-freezing  types,  it  is  advisable  to  make 
battery  shelters  or  houses  as  impervious  to  cold  as  possible. 
The  internal  resistance  of  cells  increases  with  decrease  of  tem- 
perature, and  when  the  surrounding  air  has  a  temperature  below 
that  of  freezing,  the  action  is  sluggish,  the  current  discharge 
being  low  and  the  requisite  circulation  of  the  exciting  liquid 
poor.  In  Fig.  92,  A  is  a  wooden  battery  tank  or  well  which 
may  conveniently  be  installed  below  ground,  with  the  top  pro- 
jecting above  the  surface.  The  latter  is  weatherproof  and 
provided  with  a  hinged  cover,  while  the  cells  are  arranged  in 
tiers,  upon  ventilated  shelves,  for  ease  of  inspection  and  renew- 
ing. The  inner  base  is  provided  with  drainage  holes,  the  scrap 
material  being  contained  in  suitable  boxes. 

At  B  and  C  a  sectional  and  side  elevation  of  a  common  type  of 
battery  house  is  given.  The  shelves  a  are  arranged  on  the  inside 
walls,  giving  a  maximum  of  room  for  the  batteryman's  opera- 
tions. The  walls  are  lined  with  felt,  asbestos,  or  similar  material, 
6,  for  protection  from  the  varying  temperature  of  the  outer  air. 
With  this  arrangement  inspection  is  rapid,  and  safety  from  high 
water  assured. 


CHAPTER  VII. 
THE  TRACK  CIRCUIT. 

THE  track  circuit  includes  that  part  of  the  control  feature 
which  is  affected  by  the  presence  of  a  train  within  a  block.  It 
consists  of  insulated  sections  of  track  across  which  relays  and 
batteries  are  connected  so  that  the  energization  of  the  latter 
cannot  be  effected  when  the  rails  are  connected  by  a  pair  of 
wheels  and  axle,  or  by  other  conditions  which  have  been  prede- 
termined as  dangerous  to  a  rapidly  moving  train. 

The  simplest  imaginable  track  circuit,  combined  with  an  old 
style  of  disk  signal,  is  shown  in  Fig.  93.  The  section  of  track, 


FIG.  93 

J,  is  insulated  from  the  adjacent  track  sections  by  the  insulating 
joints,  H  and  7,  and  is  connected  to  a  relay,  D,  and  battery,  C. 
The  latter  thus  energizes  D  through  the  rails  as  a  circuit.  This 
causes  the  armature,  G,  to  press  against  a  contact  in  series  with 
which  is  an  electromagnet,  E  (controlling  the  clockwork  which 
operates  a  banner  in  signal  A),  and  a  local  battery,  F.  If  a 
train  occupies  /,  D  and  C  will  be  short-circuited,  thus  deener- 
gizing  E  and  holding  the  clockworked  banner  at  danger  or  stop. 
B  is  another  similar  signal  at  the  subsequent  block;  train 
movement  being  in  an  easterly  direction. 

Continuing  the  applicatiqn  of  the  track  circuit  principle,  we 
have  in  Fig.  94  a  more  comprehensive  arrangement  for  tower 

95 


96 


AUTOMATIC  BLOCK  SIGNALS 


application  than  has  been  heretofore  considered.  A  track  relay, 
G,  controls  movements  of  the  distant  semaphore  and  is  con- 
nected through  the  track  to  battery  F.  When  the  home  signal, 
H,  is  at  clear,  the  controller,  B,  is  on  closed  circuit,  and  therefore 
determines  (depending  also  on  the  position  of  the  magnetic  cir- 
cuit controller's ^(A)  armature) the  current  which  flows  through 
the  control  electromagnet,  D,  from  battery  C. 

If  a  train  be  on  section  T,  then  the  track  relay  at  G  will  be 
deenergized,  and  the  distant  blade  will  move  to  caution.  Also, 
battery  F  will  be  short-circuited,  hence  the  armature  of  E  must 
fall,  which,  in  consequence,  demagnetizes  both  D  and  A.  If 
the  operator  should  move  the  armature  of  A  up,  it  will  not 
remain  there,  owing  to  C  being  still  on  open  circuit.  Thus  the 


FIG.  94 


home  signal  cannot  be  cleared  except  with  full  knowledge  of 
the  electrical  indications. 

Before  track  circuits  were  introduced,  track  instruments  were 
employed  to  effect  the  circuit  changes  incident  to  the  movement 
of  a  train.  In  purely  automatic  practice  they  have  been  aban- 
doned, but  are  still  used  where  track  bonding  has  not  been 
resorted  to  for  minor  electrical  purposes,  such  as  the  ringing  of 
a  bell,  or  movement  of  an  indicator.  Fig.  95  shows  this  device 
in  section,  it  consisting  of  a  hollow  upright  placed  a  short  dis- 
tance from  the  rail,  which  contains  a  rod,  C,  forced  downward 
by  a  spring  and  carrying  at  its  upper  end  a  contact  button  which 
engages  in  its  upward  position  with  the  springs,  A  and  £,  to 
which  the  circuit  wires  are  connected.  When  a  train  passes 
over  the  rail,  A  is  connected  to  B  by  the  action  of  the  lever,  D. 


THE  TRACK  CIRCUIT 


97 


These  contacts  are  in  series  with  the  device  operated,  and  were 
formerly  in  the  signal-control  circuit. 

The  track  circuit  which  would  be  afforded  by  ordinary  rails 
is  unreliable,  owing  to  the  poor  electrical  contact  of  the  fish 
plates  and  abutting  rail  ends.  It  is  evident  that  a  single  open 
contact  such  as  that  caused  by  the  scale  or  oxide  usually  covering 
rails,  would  suffice  to  break  the  electrical  continuity  of  the  track 
circuit  and  render  the  signal  system  inoperative.  Passing  trains 
and  the  consequent  vibration  serve  to  increase  this  unreliability. 
For  this  reason,  rail  bonds  are  used  to  establish  the  electrical 
connection  of  the  adjacent  rails. 


~-cast-  iron    housing 
ror/A 


FIG.  95 

In  Fig.  96  the  method  of  applying  bond  wires  to  two  butting 
rail  ends,  A  and  B,  is  shown.  The  fish-plate,  F}  is  bridged  over  or 
shunted  by  two  bond  wires,  C-C,  which  are  usually  No.  8  B.W.G. 
galvanized  E.B.B.  iron,  dependence  not  being  placed  on  the 
contact  of  the  former.  The  connection  is  effected  by  channel 
pins,  D,  one  of  which  is  shown  at  E,  these  being  driven  in  a 
-j^-inch  hole  drilled  in  the  web  of  the  rail,  with  one  end  of  the 
bond  wire.  The  channel  pin  is  recessed  and  tapered  so  that 
when  driven  home  it  grips  the  wire  with  considerable  force. 
The  wedge  compresses  tightly  around  the  wire,  thus  producing 
a  large  contact  area,  the  hole  in  the  pin  before  driving  being 
slightly  larger  than  the  diameter  of  the  wire.  The  operation  of 
driving  also  cleans  the  pin,  the  wire,  and  the  rail;  thus  affording 
a  good  electrical  contact,  which  is  impervious  to  rain  or  dust. 
A  section  of  the  rail  and  channel  pin  is  given  at  G. 


98 


AUTOMATIC  BLOCK  SIGNALS 


Riveted  bond  wires  are  sometimes  used,  although  the  consen- 
sus of  opinion  is  that  they  are  not  so  reliable  as  channel  pins. 
A  riveted  joint  is  illustrated  at  H  in  the  above  figure,  a  rivet 
being  shown  at  K,  the  latter  being  upset  in  a  hole  drilled  in  the 
flange  of  the  rail.  No.  6  B.  &  S.  copper  wire  is  used  at  planked 
highway  crossings,  tunnels,  or  other  damp  localities  when  rivets 
are  used. 

In  some  cases  bond  wires  are  placed  beneath  the  fish-plate ;  in 
others,  outside  the  latter.  The  advantages  of  the  first  are  the 
protection  afforded  the  wire  from  mischievous  persons,  who 
often  force  the  loose  wire  up  on  the  face  of  the  rail  to  be  cut  off 


H 


by  a  passing  train;  and  also  from  the  operations  of  the  main- 
tenance-of-way  corps.  The  disadvantage  is  the  ease  of  oxidiza- 
tion, caused  by  the  entrained  moisture,  and  the  labor  of  inspec- 
tion. The  second  method  has  a  reverse  order  of  advantages  and 
disadvantages. 

When  a  track  relay  fails  to  be  energized,  after  a  survey  has 
shown  that  the  track  battery  is  in  proper  condition,  it  is  neces- 
sary to  inspect  the  bond  wires  on  both  rails  of  the  entire  section, 
to  locate  the  open  circuit.  With  bond  wires  placed  beneath  the 
fish-plates,  this  is  a  laborious  process,  since  each  bond  must  be 
pulled  to  determine  its  continuity.  With  open  bonds  it  is 
merely  necessary  to  glance  at  the  wires  to  discover  any  break  in 


THE  TRACK  CIRCUIT 


99 


the  circuit,  riding  on  the  rear  of  a  train  giving  ample  time  for 
inspection. 

The  number  of  bond  wires  used  at  a  joint  is  a  matter  of  indi- 
vidual opinion,  but  usually  two  are  employed.  With  covered 
bonds,  the  general  practice  is  to  use  one,  while  at  grade  cross- 
ings, bridges,  and  tunnels,  three  are  used,  to  decrease  the  liability 
of  an  open  circuit,  due  to  the  vibration  and  moisture  evident 
under  these  conditions.  Continued  vibration  results  in  crys- 
tallization of  the  metal  at  the  junction  with  the  rail;  and  when 
a  break  occurs,  it  is  difficult  to  detect. 

A  representative  installation  at  a  switch  or  crossover  is  shown 
in  Fig.  97.  The  trunking,  A,  shown  in  section,  carries  the  insu- 
lated leads  from  the  switch  instrument,  B,  and  the  track  connec- 


FIG.  97 

tions,  E-C.  When  the  switch  is  open,  B  short-circuits  the 
track,  thus  giving  the  block  the  same  condition  as  that  obtain- 
ing when  a  train  is  in  this  section.  The  switch-point  rail  rides 
upon  two  or  more  wedge  blocks,  F,  that  prevent  it  from  coming 
in  contact  with  the  rails  at  E,  from  which  it  must  be  insulated 
when  the  switch  is  in  its  normal  position,  as  the  point  rail  is  in 
electrical  connection  with  the  rail  at  C,  through  the  uninsulated 
cross-bar,  7,  and  the  remainder  of  the  rail.  An  end  elevation  of 
B  is  given  at  G.  The  short-circuiting  action  of  the  point  rail 
cannot  be  depended  upon;  otherwise  the  switch  instrument 
would  not  be  used.  This  is  an  important  consideration,  as  the 
open  switch  must  hold  its  home  signal  at  danger. 

The  same  object  is  obtained  in  a  line-wire  system  by  opening 
the  signal  circuit  when  a  switch  is  open.    This  is  accomplished 


100 


AUTOMATIC  BLOCK  SIGNALS 


through  the  arrangement  shown  in  Fig.  98.  The  wood,  w,  is  of  a 
width  conforming  to  the  number  of  contact  springs,  n,  used.  One 
of  the  latter  is  used  for  each  of  the  circuits,  and  it  makes  and 

breaks  connection  by  its 
end,  a,  with  a  stationary 
contact  piece,  h.  This  is 
effected  by  the  small  insu- 
lated roller,  /,  which  is 
operated  by  the  switch 
movement  through  the 
FlG  98  pivoted  lever,  m.  When 

the  switch  is   closed,  the 

end,  a,  is  in  contact  with  h,  and  when  open  it  is  disengaged 
from  the  latter,  due  to  the  removal  of  the  roller  from  the  hump 
in  the  spring.  One  circuit  wire  is  connected  to  n  and  the  other 
to  h.  On  double-track  lines,  four  contact  springs,  which  are 
in  series  with  home  east,  home  west,  distant  east,  and  distant 
west,  are  often  used. 

Since  cross-bars  and  switch  rails  would  ordinarily  short- 
circuit  the  track,  it  is  necessary  that  insulation  be  introduced  in 
these  members  to  maintain  the  normal  electrical  isolation  of 
the  rails,  which  are  of  opposite  polarity.  As  the  track  voltage 
is  very  low,  the  insulation  re- 
sistance need  not  be  relatively 
high,  as  is  required  in  power 
circuits.  For  this  purpose 
fiber  is  almost  universally  em- 
ployed, due  to  its  economical 
initial  cost  and  subsesquent 
ability  to  withstand  excessive 
pressure  and  vibration.  Sev- 
eral schemes  of  switch  con- 
struction are  in  use  which 
eliminate  the  use  of  insulation 
at  these  points.  One  very 
meritorious  arrangement  was 
Fig.  97. 

In  Fig.  99  a  standard  type  of  switch-rod  insulation  is  shown. 
The  rod  is  divided  into  two  parts,  A  and  B,  the  adjacent  ends 
being  secured  mechanically  by  the  bolts,  C,  and  insulated  by  the 


FIG.  99 


described  in    connection   with 


THE  TRACK  CIRCUIT  '  101 

fiber  bushings,  E  and  strips,  D.  Adjacent  rail  ends  in  an  insulated 
track  section  are  separated  by  fiber  sheets  of  the  same  shape  as 
the  rail  section,  as  at  G.  The  rails  are  held  either  by  wood 
splice  bars,  or  the  regular  steel  fish-plates  are  supplemented  by 
fiber  sheets  conforming  to  the  rail  sides.  The  bolts  passing 
through  the  rails  are  insulated  by  means  of  fiber  bushings. 
Where  special  reinforced  fish-plates  are  used,  a  more  substantial 
disposition  of  the  sheet  fiber  is  effected. 

In  Fig.  100  an  Atlas  rail  joint  is  shown  in  section.  Such  a 
massive  construction  is  required  on  the  outer  side  of  a  curve 
for  any  rail  section,  and  is  used  on  roads  having  heavy  rails, 
such  as  90  or  100  pounds  to  the  yard. 


•fibre  insulation 


FIG.  100 

Properly  designed  insulated  joints  are  of  the  utmost  impor- 
tance in  maintaining  the  integrity  of  the  track-circuit  equip- 
ment. Great  trouble  has  been  heretofore  experienced  with  this 
adjunct,  but  experience  and  time  test  have  sifted  out  the  forms 
of  joints  that  are  fitted  for  this  purpose.  A  good  joint  will  have 
great  mechanical  strength,  stand  excessive  vibration  and  wear, 
continue  the  proper  alignment  of  the  rails,  have  high  insulation, 
and  be  easily  renewed.  Turnouts,  local  freight  lines,  sidings, 
and  secondary  tracks  are  sufficiently  well  insulated  by  wood 
splice-bars;  while  main  tracks  should  have  joints  reinforced  by 
steel  plates. 

In  completing  track  or  other  circuits  between  a  drawbridge 
and  the  abutments,  it  is  not  often  advisable  to  use  a  submarine 


102  AUTOMATIC  BLOCK  SIGNALS 


cable,  as  the  latter  is  not  only  too  costly  and  undependable, 
but  it  does  not  break  the  circuits  when  the  bridge  is  open. 
A  circuit-breaking  device,  operated  coincident  with  the  move- 
ment of  the  bridge  is  a  desirable  feature,  and  it  should  have 
sufficient  flexibility  to  prevent  misalignment  of  the  draw  from 
affecting  it.  A  so-called  bridge  circuit-coupler,  which  is  used 


FIG.  101 


FIG.  102 


to  preserve  the  continuity  of  such  circuits,  so  that  when  the 
bridge  is  open  they  will  be  opened,  is  shown  in  Fig.  101,  and 
consists  of  two  boxes,  B and  E,  containing  the  connecting  arrange- 
ments, either  of  which  may  be  movable,  one  being  fastened  to 
the  bridge  end,  and  the  other  to  a  cross-tie  at  the  rail  ends.  A 
is  fastened  to  a  lever  of  the  bridge  locking,  and  operates  the 
fingers,  C,  through  the  cross-bar,  G,  so  that  when  the  bridge  is  to 


THE  TRACK  CIRCUIT 


103 


be  opened,  the  contact  fingers,  C,  can  be  withdrawn  from  D, 
thus  breaking  the  respective  circuits.  Flexible  cables,  F,  allow 
a  wide  range  of  movement  of  C,  the  bridge  circuits  being 
completed  through  the  binding  contacts,  H. 

One  method  of  installing  track  cells  and  relays  is  shown  in 
Fig.  102.  Within  the  cast  iron  chute,  C  (which  is  embedded  in 
the  earth  near  the  track  to  such  a  depth  that  only  about  one 
foot  of  the  top  appears  above  ground),  the  three  cells,  /,  held  in 
a  wooden  cage,  H,  are  placed.  This  cage  is  raised  and  lowered 
by  the  rope,  G.  The  wires,  K,  leading  from  the  cells  pass  to 
the  track  by  way  of  the  trunking,  F.  Other  wires,  E,  within  the 
hollow  upright,  B,  pass  from  the  relays,  R,  to  the  track.  These 
relays  are  placed  upon  the  shelves,  S,  and  in  the  design  given 


FIG.  103 


FIG.  103  a 


are  of  the  polarized  and  neutral  types.  The  number  of  wires, 
M,  will  vary;  in  a  double-track  system  there  would  be  ten  or 
twelve,  although  eight  only  are  shown  in  the  figure,  which  is 
for  single-track.  The  number  also  varies  accordingly  as  the 
section  is  at  a  signal  or  not ;  in  the  former  case  more  wires  being 
used.  For  the  batteryman's  convenience  and  for  protection, 
a  cover,  D,  provided  with  a  lock,  L,  is  added.  The  casing,  A, 
is  of  cast  iron,  and  both  water  and  insect  proof.  Sometimes  the 
track  chute  is  separate,  consisting  of  a  simple  cast-iron  cylinder. 
At  K  a  connector,  which  is  soldered  to  the  leads  at  the  cells, 
is  shown.  The  groove  at  the  side  is  for  the  reception  of  the 
soldered  wire. 

In  Fig.  103  the  relay  and  track  connections  at  a  cut  section 
on  a  normal  clear,  wireless,  two-arm  home  and  distant  system 
appear,  the  diagram  of  circuits  being  given  at  A.  P  is  a  polarized 


104 


AUTOMATIC  BLOCK  SIGNALS 


relay  having  two  contacts  in  multiple  on  both  polar  and  neutral 
armatures.  The  track  battery,  B,  has  two  components,  the 
greater  ampere-hour  capacity  (of  a  given  polarity)  being  con- 
nected to  the  track  during  the  normal  operation,  which  is  when 
the  semaphores  are  at  clear.  When  a  train  occupies  either  sec- 
tion C  or  E,  section  E  will  be  short-circuited  by  the  action  of 
the  neutral  armature  contacts  when  the  magnets  are  deener- 
gized.  When  the  distant  blade  at  the  preceding  signal  is  at 
caution,  the  ampere-hour  capacity  (at  the  opposite  polarity)  of 
the  connected  track  battery,  B,  is  least,  since  this  occurs  only 
when  a  train  occupies  the  distant  section. 

In  Fig  104  the  track  and  other  connections  at  a  normally 
clear  wireless,  with  overlap,  banjo-disk  home  signal,  S,  are 
shown.  R  is  a  polarized  relay,  the  distant  signal  being  placed 


FIG.  104 

at  a  relayed  cut  section.  Such  a  scheme  of  connection  is  also 
used  for  a  distant  with  a  home  in  the  rear,  the  latter  having 
a  separate  distant  signal.  An  electromagnet  energizes  the  disk 
armature,  this  magnet  having  two  windings,  one  of  high  resis- 
tance, and  the  other  of  low  resistance.  The  high-resistance  coil 
is  connected  in  shunt  with  the  contacts  of  the  normally  open 
spring-switch,  E.  When  the  signal  is  at  danger  this  shunt  is 
closed,  thus  short-circuiting  the  high-resistance  coil  and  leaving 
in  circuit  the  low-resistance  winding.  This  produces  a  high  initial 
current  discharge,  and  consequent  torque,  when  the  front  contacts 
at  the  relay  are  closed,  insuring  the  proper  clearing  of  the  ban- 
ner. When  once  cleared,  the  latter  can  be  held  in  this  position 
by  the  low  energy  of  the  high  resistance  winding.  At  the  connec- 
tion points,  B  is  the  free  battery  terminal,  and  C  the  common. 


CHAPTER  VIII. 
CONTROLLED   MANUAL  SYSTEMS. 

IN  the  manual  system  of  block  signaling,  the  signals  are 
operated  and  controlled  solely  by  the  tower  attendant,  there 
being  no  automatic  control  of  the  indicating  functions.  In  the 
controlled  manual  system,  which  is  intended  for  long  block  sec- 
tions, the  movements  of  the  signals  are  effected  by  the  operator, 
but  these  movements  are  controlled  by  electrical  devices  whose 
sources  of  current  are  in  various  track  and  line  circuits. 

In  its  usual  form,  this  latter  system  consists  of  a  number  of 
electromagnets  whose  moving  systems  are  so  mechanically 
connected  to  the  levers  they  control,  that  movement  of  the 
latter  is  prevented  unless  the  block  covered  is  in  the  proper 
condition  for  such  movement.  This  is  effected  by  giving  the 
operator  at  one  end  of  the  block  electrical  control  over  the  lever 
movement  at  the  other  end. 

Thus,  if  the  operator  at  17  allows  the  movement  of  a  train  to 
18,  and  then  throws  his  signal  to  the  danger  position,  he  cannot 
throw  the  latter  to  clear  until  the  operator  at  18  unlocks  his 
lever  (17's),  which  18  will  not  do  until  the  train  has  passed  out 
of  the  block,  automatic  arrangements  preventing  this  unlocking, 
even  if  it  were  attempted.  These  latter  accomplish  this  object 
by  an  electromagnet  controlling  the  lever  at  17,  in  series  with 
which  is  a  battery  at  18,  the  line  wire  of  this  circuit  being 
either  broken  at  one  of  the  various  cut  sections  of  the  block, 
or  at  the  section  of  the  next  block  at  18,  which  has  a  track- 
relay  back-contact  in  series  with  this  battery,  so  that  the 
locking  magnet  is  not  demagnetized  until  a  train  enters  this 
section. 

This  latter  arrangement  is  given  in  diagrammatic  form  in  Fig. 
105.  Track  relay  6,  at  section  18a,  normally  holds  its  armature 
in  the  position  shown.  When  a  train,  passing  from  17  to  18, 
arrives  at  18a,  by  short-circuiting  track  battery  c,  Us  armature 

105 


106 


AUTOMATIC  BLOCK  SIGNALS 


closes  the  circuit  of  d,  thus  energizing  a  and  releasing  the  locking 
function,  e. 

Under  the  permissive  system,  however,  this  arrangement 
would  not  give  adequate  protection,  for,  should  a  train  be 
allowed  to  pass  17  before  the  previous  train  has  reached  18,  then 
when  the  latter  arrives  at  18  the  locking  function  at  17  is  released, 
thus  giving  a  clear  signal  to  the  next  train  entering  front  section 
17-18.  To  prevent  this  confusion,  a  track  relay  and  contacts 
may  be  interposed  in  the  latter  section,  thereby  approaching 
more  closely  to  an  automatic  system.  This  would  be  disadvan- 
tageous, however,  in  taking  away,  in  this  case,  the  requisite 
control  of  conditions  from  the  tower  operator. 

In  the  manual  control  system  brought  out  by  Coleman,  a  com- 
bined track  and  wire  circuit  is  used  to  control  the  movement  of 


d 

iiiiiiii 

f 

@ 
e 

J7 

18 

~~® 

t  

^ 

*7s  o.    i 

FIG.  105 

mechanical  signals.  This  arrangement  will  now  be  outlined, 
but  not  the  actual  mechanical  construction  of  the  devices  used; 
the  relations  of  the  circuits  and  functions  to  automatic  circuits 
being  the  principal  object  of  this  description. 

In  Figs.  106,  107,  and  108  the  arrangement  of  connections 
and  a  diagrammatic  representation  of  the  functions  of  the  appa- 
ratus is  shown.  Fig.  106  gives  the  circuits  at  the  first  block 
station  considered;  Fig.  107,  at  the  second  station;  and  Fig. 
108,  at  the  third  station,  the  fourth  and  all  subsequent  stations 
being  entirely  similar  to  the  third  in  the  arrangement  of  accesso- 
ries and  circuits. 

In  Fig.  106  signal  arm  5,  controlling  the  home  block,  is 
operated  by  lever  1,  which  is  pivoted  at  2,  through  the  inter- 
position of  the  usual  mechanical  accessories,  and  also  the  electric 
slot,  13.  This  slot  prevents  electrically  the  movement  of  the 


CONTROLLED  MANUAL  SYSTEMS 


107 


signal  arm  when  unfavorable  conditions  exist,  as  will  be  shown 
later.  The  locking  arrangement  consists  partly  of  a  sector 
casting,  6,  having  a  lug,  10,  which  is  connected  by  a  link  to  the 
slotted  section,  18,  the  latter  being  moved  whenever  the  signal- 
man, by  squeezing  the  hand  piece,  3,  attempts  to  unlock  the 
lever  and  subsequently  throw  the  latter.  The  movement  of  the 
sector  is  governed  by  the  electromagnet,  9,  through  the  finger,  7, 
and  the  links,  8,  connected  to  its  armature. 

In  addition  to  9,  there  is  a  circuit-control  electromagnet,  12, 
and  also  the  relay,  14,  connected  to  the  track.  The  arrangement 
of  accessories  at  station  2  is  somewhat  similar  to  the  above,  and 


common 


FIG.  106 

contemplates  in  addition  a  sliding  semaphore,  26,  and  a  switch, 
19.  The  connections  of  the  electric  slot  at  this  signal  are  not 
shown,  as  it  should  be  remembered  that  these  circuits  are  traced 
out  only  so  far  as  they  affect  the  signal  at  station  1. 

The  electromagnet,  9,  is  connected  in  series  with  the  line  wires 
and  with  one  of  the  front  contacts  of  the  track  relay,  14.  The 
line  wires  pass  to  the  make  and  break  arrangement  20,  operated 
indirectly  by  the  switch  lever  at  station  2,  the  battery,  21,  being 
in  this  circuit;  hence  9  will  not  be  energized  unless  the  sector 
block,  22,  is  in  the  normal  or  danger  position,  as  shown.  The 
circuit  of  9  will  thus  be  broken  at  20,  and  finger  7  will  prevent 
motion  of  the  sector  block,  6,  thus  effectually  locking  signal  5  in 
the  danger  position. 


108 


AUTOMATIC  BLOCK  SIGNALS 


Hence,  before  5  can  be  cleared,  the  operator  is  required  to 
summon  the  operator  at  station  2  to  put  his  signal  in  the  normal 
or  stop  position.  Thus  the  apparatus  requires  that  the  block 
covered  by  5  be  closed  at  its  outgoing  end,  thereby  preventing 
a  train  from  receiving  a  single  permission  to  pass  through  two 
blocks.  When  a  train  is  to  pass  from  1  to  2,  all  conditions  being 
favorable,  the  operator  throws  lever  1,  and  consequently  signal 
5,  the  train  then  passing  this  signal.  This  causes  the  track 
battery  25  to  be  short-circuited,  thus  deenergizing  relay  14, 
thereby  breaking  the  circuit  of  9.  This  allows  the  finger,  7,  to 
drop,  preventing  motion  of  sector  block  6,  and  consequent 


Com  mo •??> 


FIG.  107 

unlocking  of  the  lever.  Thus  signal  5  cannot  be  thrown  to  the 
clear  position  until  the  train  has  passed  out  of  the  block  and 
restored  contact  16  to  its  normal  position  by  removing  the 
short  circuit  from  the  battery. 

Since  the  train  cannot  pass  out  of  the  block  until  the  signal,  23, 
has  been  cleared,  it  follows  that  when  this  occurs  the  circuit  of  9 
will  be  opened  at  20;  hence,  before  the  signal,  5,  at  station  1  can 
be  again  cleared,  the  train  must  pass  out  of  the  block  of  23,  and 
23  must  be  thrown  to  the  danger  position.  It  is  evident  that  a 
careless  operator  might  throw  the  signal  at  station  1  to  the  clear 
position,  and  thus  allow  another  train  to  enter  the  block  before 
the  first  had  passed  out  of  it.  But  this  is  prevented  by  the 


CONTROLLED  MANUAL  SYSTEMS 


109 


action  of  the  electric  slot,  which  throws  the  signal  to  the  stop 
position  when  a  train  has  entered  its  block  independently  of  the 
operator.  Thus  the  connection  between  the  lever  and  the  sema- 
phore is  not  positive,  but  depends  upon  the  electrical  conditions 
of  the  block.  The  circuit  of  this  slot  (which  is  operated  by  an 
electromagnet)  is  composed  of  the  wire,  4,  the  second  front 
contact  of  track  relay  14,  electromagnet  12,  armature  contact 
27,  battery  17,  common  line-wire,  and  wire  28. 


FIG.  108 

When  a  train  enters  the  block  of  signal  5,  track  relay  14  is 
short-circuited,  thus  breaking  the  slot  magnet  circuit  at  15,  and 
simultaneously  at  27.  This  causes  5  to  pass  to  the  danger  posi- 
tion, independent  of  the  position  of  lever  1.  The  reason  for 
interposing  the  independent  double  break  is  to  preclude  the 
possibility  of  the  operator's  throwing  forward  the  lever  to  the 
normal  position  as  soon  as  the  train  has  passed  into  the  block 
protected  by  23,  as  this  latter  position  of  the  train  will  restore 
the  break  in  the  circuit  at  15  by  the  action  of  14.  Thus  the 
connection  between  the  lever  and  its  semaphore  is  effectually 
broken  until  the  proper  conditions  obtain.  The  consent  of  the 


110  AUTOMATIC  BLOCK  SIGNALS 

operator  at  2  to  allow  movement  of  the  signal  lever  at  1  is  usually 
given  by  an  electric  bell  or  telegraph  code. 

It  is  evident  that  the  circuit  cannot  be  closed  at  27  except 
by  a  current  passing  through  the  circuit  independent  of  its 
own  armature  and  contact.  This  latter  circuit  is  formed  by  the 
wire,  4,  passing  from  the  slot  magnet  of  13,  and  includes  also 
make-and-break  arrangement  15,  magnet  coils  12,  make-and- 
break  mechanism  11,  battery  17,  common  line-wire,  and  wire 
28.  Since  11  is  controlled  by  sector  block  6,  and  the  links, 
10,  attached  to  18,  when  the  lever,  1,  has  been  thrown  to  its  nor- 
mal or  stop  position,  the  circuit  is  closed  at  this  point,  it  being 
open  when  5  is  in  the  clear  position. 

The  motion  of  the  hand  piece,  3,  which  is  necessary  in  order 
that  the  lever  may  be  unlocked  preparatory  to  its  movement, 
produces  motion  in  the  slotted  casting,  18,  which  indirectly 
breaks  the  circuit  at  11,  providing  the  sector  block,  6,  does  not 
meet  with  the  free  end  of  the  finger,  7.  The  closing  of  the  cir- 
cuit at  11  causes  a  current  to  pass  through  the  coils  of  12, 
thereby  closing  the  circuit  of  slot  13  at  27.  This  becomes 
necessary  in  order  that  the  slot  mechanism  may  be  held  locked 
when  lever  1  is  to  be  moved.  Otherwise  the  signal  could  not 
be  cleared,  since  the  mechanical  connection  is  through  the 
interposition  of  the  slot.  As  27  is  in  shunt  with  11,  the  circuit 
is  not  broken  by  the  opening  of  11,  so  that  the  current  from  17 
continues  to  pass  around  the  coils  of  12. 

As  already  stated,  this  system  is  applied  to  block  sections  of 
great  length,  so  that  if  a  continuous  rail  circuit  were  used,  it 
would  become  needlessly  expensive  and  complicated.  As  this 
combination  of  wire  and  track  circuits  is  more  readily  compre- 
hended, and  simplifies  what  will  follow,  the  above  description 
has  included  it.  In  the  circuits  given  with  those  at  station  3, 
the  track  circuit  will  be  omitted,  except  for  a  short  working  or 
setting  length  at  each  signal. 

It  has  been  shown  that  when  a  train  passes  signal  23  the  con- 
trol of  5  is  restored  to  the  operator  at  station  1,  provided  the 
operator  at  2  has  put  his  lever  in  the  normal  position.  At  sta- 
tion 3,  on  the  other  hand,  23  cannot  be  unlocked  at  once  by  the 
passing  train,  only  the  plunger,  58,  being  released.  This  latter 
must  be  actuated  by  the  operator  before  the  train  passing  signal 
23  can  short-circuit  the  track  relay  and  produce  an  automatic 


CONTROLLED  MANUAL  SYSTEMS  111 

set  of  conditions  at  station  2.  The  operator  at  station  3  must 
actuate  the  plunger,  58,  at  the  request  of  the  operator  at  station 
2,  so  that  the  latter  may  give  a  clear  signal  to  the  next  train  to 
occupy  the  block.  In  addition,  the  former  must  throw  his  sig- 
nal to  danger. 

Since  a  train  cannot  pass  34  until  23  is  cleared,  and  since  23 
has  been  placed  in  the  danger  position  to  allow  of  5's  being 
unlocked,  it  cannot  be  thrown  to  the  clear  position  without  the 
permission  of  the  operator  at  station  3.  The  apparatus  by 
which  this  permission  is  given  constitutes  Coleman's  machine, 
the  mechanical  construction  of  which  will  not  be  taken  up. 

Again  considering  the  arrangement  at  station  3,  it  is  evident 
that  lever  35  cannot  be  thrown  until  the  sector  block,  36,  can 
clear  37;  that  is,  until  a  current  passes  through  the  electro- 
magnet, 38.  The  floor  knob,  39,  is  then  pressed  downward, 
which  closes  the  contacts  at  40  and  connects  one  side  of  38  with 
the  common  line-wire.  When  this  occurs,  we  may  trace  up  the 
circuit  to  the  closed  contacts  at  41  and  the  open  contacts  at  42. 
These  latter  must  be  closed  by  energizing  the  electromagnet,  43, 
before  the  circuit  can  be  completed  through  the  battery,  64,  and 
the  common  line  return.  As  43  is  in  shunt  with  the  binding 
posts,  44  and  45,  a  current  must  come  in  over  the  line  wires  from 
station  2,  and  on  the  common  line  side  through  the  armature 
contacts  of  relay  52.  Hence,  it  is  necessary  that  52  be  in  an 
energized  condition,  that  is,  with  no  train  on  the  section  of  track- 
battery  53.  At  station  2,  20  must  be  closed,  then  a  current  from 
21  will  flow  through  43.  With  these  conditions  fulfilled,  51  can 
be  cleared  by  throwing  35. 

As  above  stated,  58  is  a  plunger  which  is  moved  in  the  direc- 
tion of  the  arrow,  normally  held  in  the  extreme  inner  position  by 
a  spring,  70,  this  plunger  being  provided  for  the  purpose  of  allow- 
ing the  signal  at  the  next  station  to  be  unlocked.  When  58  is 
pulled  out  to  the  position  shown,  the  projection  on  the  dog,  57, 
drops  within  the  aperture,  71,  in  58,  thus  breaking  the  contact  of 
spring  55  with  54,  and  connecting  56  with  54.  The  spring  con- 
tacts, 59,  are  closed,  at  the  same  time  those  at  41  being  opened. 
The  former  is  effected  by  the  action  of  the  rock  shaft  carrying 
the  dog,  57,  and  the  latter  by  the  movement  of  a  train. 

The  resistance  coil,  69,  is  interposed  in  the  circuit  of  61,  while 
61  is  an  electromagnet  which  has  an  armature  provided  with  a 


112  AUTOMATIC  BLOCK  SIGNALS 

swinging  carrier,  62.  When  60  is  energized,  its  armature,  63, 
which  carries  a  retaining  catch,  closes  the  contacts,  68,  thus 
connecting  48  with  49.  When  37  is  raised  by  38,  the  contacts  of 
65  are  opened,  thus  disconnecting  47  from  64.  When  the  train 
passes,  52  is  energized,  and  its  armature  closes  the  lower  contact, 
the  operator  returning  the  lever  to  its  normal  position.  This 
opens  the  retaining  circuit  at  66,  and  in  consequence,  electro- 
magnet 60,  releasing  the  catch  63,  allowing  the  word  "  Free  " 
on  a  banner  to  pass  before  a  glass  aperture  in  the  housing,  which 
denotes  that  the  lever  at  station  2  may  be  unlocked  for  a  second 
train.  Thus  the  dependence  of  one  operator  upon  the  other  is 
shown.  By  tracing  up  the  circuits,  the  reader  will  be  able  to 
deduce  the  remainder  of  the  functions.  A  complete  description 
of  the  apparatus  would  be  too  lengthy  for  this  book. 

On  single-track  lines,  a  modified  form  of  lock  and  block  arrange- 
ment must  be  used  if  the  controlled  manual  system  is  employed. 
Trains  bound  in  both  directions  must  run  alternately  into  sidings 
to  allow  passing,  these  sidings  being  governed  by  signals  which 
are  interconnected  electrically.  Block  towers  are  placed  as 
near  as  convenient  to  overlapping  opposite  sidings,  into  which 
trains  proceed  under  given  conditions.  The  operator  at  block 
tower  23,  for  example,  governs  the  levers  at  24,  this  consecutive 
arrangement  being  necessary  for  safety.  It  is  evident,  also, 
that  each  operator  has  control  over  trains  moving  in  both 
directions. 

In  Fig.  109  the  relation  of  such  a  single-track  system,  with 
the  Leonard  scheme  of  control,  is  shown.  D  is  a  track  instru- 
ment (a  device  which  closes  a  circuit  when  the  wheels  of  a  train 
pass  over  the  end  of  a  projecting  lever  whose  other  end  operates 
a  spring  contact,  as  in  Fig.  95)  which  closes  the  circuit  of  the 
battery,  F,  through  the  lock  instrument,  E.  In  this  same  circuit 
is  a  circuit  breaker,  G,  which  disconnects  E  from  F.  A  circuit 
closer,  A,  is  situated  at  the  ends  of  the  east-  and  west-bound 
sidings,  and  is  connected  to  E  and  F  by  the  line  wires,  K,  L. 
(The  west-bound  apparatus  is  distinguished  by  small  letters.) 

The  operator,  to  allow  an  east-bound  train  to  proceed  from 
23,  unlocks  the  signal  lever  at  the  latter  point.  The  unlocking 
current  passes  over  the  line  wires  w,  which  connect  successive 
towers.  This  function  then  remains  locked  until  released  by 
the  track  instrument,  due  to  the  effect  of  the  passing  train. 


CONTROLLED  MANUAL  SYSTEMS 


113 


The  line  circuit  at  the  same  time  is  opened  (by  the  circuit 
breaker,  G,  of  the  signal  C),  so  that  a  west-bound  train  cannot 
enter  the  section,  because  the  west-bound  signal,  B,  is  at  danger, 
it  being  controlled  by  the  battery  at  23.  If  the  locking  function 
is  not  released  by  Dy  the  train  enters  the  side  track,  and  the 
switch,  S,  must  be  closed  by  the  brakeman  immediately  after 
the  train  passes  the  derailing  switch,  which  is  at  A.  This 
operation  closes  for  an  instant  the  unlocking  circuit  at  A, 
which  sends  a  current  to  the  lock  instrument  from  the  battery,  F. 
If  a  west-bound  train  is  to  be  allowed  to  proceed,  permis- 
sion and  unlocking  is  first  received  from  25.  The  signal,  C,  is 
then  cleared,  which  breaks  the  circuit  of  the  track  instrument 


"3            ^x.^ 

S.  n  ni 

.  fan  jSTX*rs 

K 

L 

*LJ     _j 

XiiJ  ^ 

kw    ^S\  Jf 

^^Twest  b'ound  C-«  —  ^>T  1 

S       sid  i 

"3     t  oJ  1 
a 

k  A 

^jH 

^  7 

_  ^         N^  

W              Tower  2V             W 
FIG.  109 

and  prevents  the  signal  from  being  unlocked  by  a  train  until 
it  has  first  been  thrown  to  the  stop  position.  Indicators  are 
used  at  the  switches  to  apprise  the  conductor  as  to  whether 
he  may  proceed  on  the  main  line  or  take  a  siding. 

The  electric  slot  is  a  controlling  device  which  automatically 
causes  a  mechanical  semaphore  to  move  to  the  danger  position 
after  a  train  has  passed  this  signal.  This  arrangement  pre- 
vents negligence  on  the  part  of  the  signal  operator  causing  a 
rear  end  collision.  Its  function  is  thus  similar  to  the  rod  slot 
which  has  been  in  use  for  many  years  on  purely  mechanical 
systems.  Fig.  110  represents  the  application  of  a  Union  electric 
slot  to  a  triple-lens  mechanical  signal.  The  semaphore,  S,  is 
secured  to  a  pivoted  casting  carrying  three  lenses,  L,  night 


114 


AUTOMATIC  BLOCK  SIGNALS 


indications  being  given  by  the  lamp,  A,  the  white  light  from 
which  must  pass  through  a  lens  when  the  signal  is  in  a  full  or 
partial  stop  position. 

This  blade  is  operated  by  the  rod,  C,  which  passes  into  the 
slot  box,  D,  and  is  connected  mechanically  (when  a  train  is 
not  in  the  block  of  the  signal)  with  the  rod,  C.  The  latter 


-u 


FIG.  Ill 


is  pivoted  to  a  rocking  lever  counterweighted  at  F,  which  is 
connected  to  the  signal  lever  by  the  steel  wires,  G.  E  is  a  circuit 
controller  connected  to  the  slot  or  control  circuit  of  other  signals, 
as  will  be  shown  later. 

The  slot  structure  and  its  weatherproof  housing  is  shown  in 
part  section  and  part  elevation  in  Fig.  Ill;  1  being  a  side  and 
2  a  front  view.  When  motion  is  imparted  to  the  rod,  H,  by 


CONTROLLED  MANUAL  SYSTEMS  115 

the  signalman,  the  frame,  F,  and  the  accessories  attached  to  it 
move.  The  rods,  R  and  H,  are  not  connected  unless  the  electro- 
magnet, M,  is  energized,  when  the  signalman  has  full  control 
of  the  semaphore.  On  the  other  hand,  if  M  be  deenergized, 
the  connection  between  R  and  H  is  broken  and  movements 
of  the  latter  will  in  no  wise  affect  the  former,  hence  the  blade 
cannot  be  moved. 

To  the  frame,  F,  the  electromagnet,  M,  spring  S,  pivots  P, 
and  guide  sleeve,  F,  are  secured.  The  link,  /,  moves  around 
the  upper  pivot  as  a  center,  while  the  spring  piece,  A,  by  pressing 
against  the  projection,  B,  holds  7  in  the  position  given.  The 
roller,  W,  which  is  attached  to  7,  engages  in  a  recess  with  the 
pawl,  Q,  the  latter  being  pivoted  in  a  recess  on  the  rod,  72,  at  T. 
When  current  is  not  passing  through  M,  the  centers  of  T,  W, 
and  p  are  not  in  the  same  straight  line.  Therefore,  if  a  pressure 
be  applied  upward  on  H  (which  will  occur  when  the  signalman 
attempts  to  clear  the  signal),  the  roller  will  move  to  the  left  by 
the  action  of  the  link,  7,  on  its  pivot.  Hence  this  roller  disen- 
gages with  the  pawl  (which  cannot  move  further  to  the  left)  due 
to  the  weight  of  the  unbalanced  semaphore;  and  77  moves  up  or 
down  without  engagement.  The  electromagnet  has  a  movable 
armature,  which  is  held  at  one  end  by  the  stationary  pivot,  K, 
and  at  the  other  end  by  a  movable  pivot,  N.  0  is  a  short  link 
secured  rigidly  to  the  lever,  a,  these  being  pivoted  at  P.  The 
armature  is  normally  held  upward,  and  away  from  the  pole 
tips  by  the  spring,  L.  The  pivots,  K,  N,  and  P,  are  normally 
out  of  line,  hence,  when  an  attempt  is  made  to  force  W  upward, 
a  allows  Q  to  be  disengaged,  thereby  preventing  motion  of  R. 

If  M  be  energized,  due  to  the  block  protected  by  the  signal 
being  clear,  the  tension  of  L  will  be  overcome  and  the  armature 
will  be  in  its  extreme  lower  position.  This  forces  the  roller  into 
the  recess  in  Q,  and  if  movement  be  imparted  to  H,  Q  will  also 
move,  and  consequently  R.  If  this  motion  were  too  rapid, 
due  to  too  energetic  motion  of  the  signal  lever,  it  is  evident 
that  the  inertia  of  the  parts  would  in  all  probability  break  some 
part  of  the  mechanism.  To  prevent  this  occurrence,  a  damping 
cylinder  or  dashpot  is  interposed.  It  consists  of  a  shell,  D, 
having  a  carefully  fitted  plunger,  P,  the  latter  being  stationary, 
and  pivot  ally  secured  to  the  bolt,  V.  The  shell  is  fastened  to 
the  coupling,  U,  connected  to  the  semaphore  rod,  and  has  an 


116 


AUTOMATIC  BLOCK  SIGNALS 


extension,  Z,  which  is  slotted  and  forms  a  guide  with  the  bolt, 
V.  An  adjustable  valve,  X,  through  which  the  entrained  air 
(on  the  downward  motion)  bleeds  out  with  more  or  less  rapidity, 
according  to  the  retardation  desired,  is  provided;  and  a  shell,  E, 
forms  a  protection  from  the  weather.  The  case,  C,  is  bolted  to 
the  signal  mast  by  the  lug,  G. 

When  R  is  moved  upward,  the  entire  frame  and  its  appurte- 
nances, such  as  the  magnet  and  pawl,  also  move.  The  spring,  A, 
only  presses  upon  B  at  the  commencement  of  the  motion,  so 
that  in  case  M  were  demagnetized  by  the  presence  of  a  train  in 
the  block  or  an  opened  switch,  when  the  signal  was  at  clear,  its 
armature  would  rise,  and  the  pawl  be  released,  thus  causing  the 
signal  to  assume  the  danger  position  independent  of  the  operator. 
The  latter  then  replaces  his  lever  upon  receiving  the  indica- 
tion by  the  action  of  the  circuit  controller.  If  the  signalman 
attempted  to  throw  the  signal  to  the  clear  position,  he  could  not 
succeed,  since  H  has  no  connection  with  R.  However,  H,  M, 
F,  and  the  roller  will  move  upward,  but  this  does  not  affect  the 
semaphore's  position.  The  electric  slot  and  its  modification 

occupies  an  important  position 
in  composite  manual  and  auto- 
matic signaling,  and  is  employed 
extensively  on  signals  governed 
from  centralized  towers. 

The  method  of  applying  circuit 
controllers  to  the  levers  of  the 
controlled  manual  and  semi-auto- 
matic systems  is  shown  in  Fig. 
112.  The  lever,  Af,  pivoted  at 
H,  has  two  extensions,  F  and 
G,  to  which  the  wires  or  bars 
operating  the  signal  are  secured. 
In  order  to  unlock  this  lever,  the 
latch  must  be  opened  by  moving 
the  pivoted  member,  L,  in  the 
direction  of  the  small  arrow. 
N  is  an  electric  lock  or  slot, 
connected  by  a  link  to  one  of  the  rock  shafts  of  the  interlock- 
ing machine,  7.  This  rock  shaft  is  also  linked  to  the  unlocking 
segment  of  the  lever  by  the  rod,  E. 


~L 


D' 


CONTROLLED  MANUAL  SYSTEMS 


117 


G  and  D  are  circuit  controllers  operated  respectively  by  the 
toes,  0  and  M.  B-K  is  a  floor  button  which  closes  a  circuit 
connected  to  the  distant  cabin,  and  serves  as  a  means  of  com- 
munication and  releasing  between  the  operators.  The  functions 
and  operation  of  this  arrangement  will  be  apparent  from  de- 
scriptions already  given. 

One  application  of  a  duplex  rotary  circuit-controller,  E,  is 
shown  in  Fig.  113,  it  being  fastened  to  the  signal  pole  and 
operated  through  the  home  semaphore  by  the  rod  or  connecting 
link,  M.  7  is  a  mechanically  operated  home  and  distant,  the 
electric  slots,  A  and  C,  securing  the  semi-automatic  control,  and 
being  energized  by  battery  D  through  the  interposition  of  the 


FIG. 113 

polarized  relay,  G.  A  is  controlled  by  the  neutral  armature,  F, 
and  C  by  both  the  polarized,  N,  and  neutral  armatures  in  series. 
The  controller,  B,  is  in  series  with  the  home  slot,  and  by  being 
open  when  the  semaphore  is  not  at  clear,  effects  a  saving  in 
current  consumption,  besides  giving  an  additional  manual  con- 
trol if  desirable. 

When  the  home  blade  is  at  stop,  contact  B  is  open,  hence  C  is 
deenergized,  so  that  the  distant  cannot  be  cleared  unless  the 
former  is  clear;  a  similar  condition  existing  when  either  F  or  N 
is  open,  which  will  occur  if  T  is  short-circuited  or  of  the  wrong 
polarity.  Contacts  a  and  b  effect  a  polarity  reversal  of  the 
track  battery,  /,  by  motion  of  M .  This  polarity  change  occurs 
at  every  motion  of  the  home  blade,  thus  controlling  the  preced- 
ing signal.  The  fourth  contact  of  the  controller  is  unconnected, 


118 


AUTOMATIC  BLOCK  SIGNALS 


the  construction  allowing  a  nearly  complete  stroke  of  M  before 
a  change  in  connection  takes  place. 

A  circuit  controller  for  operation  by  the  foot  is  shown  in  sec- 
tion and  elevation  in  Fig.  114.    To  the  floor  or  other  convenient 

support,  B,  the  pivoted  lever  or 
foot  piece,  A,  is  secured.  The 
opposite  end  of  this  foot  piece 
carries  a  roller,  H,  which  presses 
against  a  curved  spring  strip,  G. 
Normally,  G  is  in  contact  with 
F,  or  E  is  connected  to  D. 
When  A  As  forced  downward, 
E  is  connected  to  C,  and  D  is 

open-circuited.  This  device  is  applied  wherever  it  is  desired  to 
close  one  circuit  simultaneously  with  the  opening  of  a  normally 
closed  circuit. 


FIG.  114 


CHAPTER  IX. 
MOTORS,  RELAYS,  ETC. 

SIGNAL  motors  are  of  small  size,  series  wound,  and  for  direct 
current  only.  As  they  are  generally  operated  by  battery  cur- 
rent, the  terminal  voltage  is  of  necessity  low.  It  is  not  prac- 
ticable to  operate  motors  over  line  wires  of  any  great  length, 
owing  to  the  great  loss  of  energy  in  the  latter,  and  the  low 
starting  torque  of  the  motor. 

The  sizes  of  motors  used  vary  from  65  to  150  watts,  or  one- 
twelfth  to  one-fifth  of  a  horse-power.  From  10  to  20  Edison 
or  Gordon  cells  are  used  to  operate  these  motors,  so  that,  should 
the  applied  voltage  vary  from  7  to  14,  the  full-load  current 
will  vary  from  9  to  5  amperes  in  the  smallest  motors  to  from 
20  to  11  amperes  in  the  one-fifth  horse-power  unit.  The  larger 
motors  (as  in  all-electric  systems  of  interlocking)  are  supplied 
with  current  from  a  storage  battery  having  considerable  poten- 
tial, so  that  the  above  currents  are  much  reduced.  Derailing 
and  switch  movement  motors  are  at  a  maximum  of  about  one 
horse-power,  although  they  operate  normally  at  about  420 
watts  (7  amperes  at  60  volts,  or  4  amperes  at  110  volts). 

In  Fig.  115  a  standard  form  of  signal  motor  is  illustrated. 
F  is  the  laminated  field,  which  consists  of  a  large  number  of 
stampings  of  soft  iron  held  firmly  between  heavy  end  pieces  of 
similar  contour.  The  exciting  coils,  W,  are  connected  in  series 
with  the  armature,  A,  through  the  brushes  B,  and  the  commu- 
tator, C.  S  is  a  removable  transparent  glass  end-shield,  which 
effectually  prevents  dust  and  moisture  from  collecting  on  the 
moving  surfaces,  also  allowing  inspection  from  time  to  time. 
P  is  the  brake  pulley  and  M  the  brake  mechanism,  whose  func- 
tion is  described  in  connection  with  Fig.  117. 

The  laminations  of  soft  iron  on  both  armature  and  field, 
having  a  high  permeability,  allow  of  a  greater  flux  density 
than  could  be  obtained  from  solid  iron,  at  the  same  time  reduc- 

119 


120 


AUTOMATIC  BLOCK  SIGNALS 


ing  to  a  minimum  the  eddy-current  loss.  The  armature  shaft 
carries  a  pinion  which  engages  with  the  gear  train  of  the  clearing 
mechanism.  The  motor  is  provided  with  a  base  by  means  of 
which  it  is  bolted  to  the  frame.  Semaphore  signals  in  general 
use  motors  that  have  become  the  standard  for  small  sizes  in 
electrical  power  application,  with  but  slight  modification. 

There  are  a  number  of  combined  electrical  and  mechanical 
methods  of  applying  a  brake  to  a  motor  armature  for  the 
purpose  of  rapidly  bringing  it  to  rest;  so  that  the  semaphore 
movement  will  occur  within  a  minimum  time  and  at  a  uniform 


FIG. 115 

rate  throughout  the  entire  angle  of  motion.  Obviously  the 
most  effective  arrangement  will  operate  immediately  upon  cur- 
rent cessation,  and  release  upon  the  commencement  of  its  flow. 
Two  such  schemes  will  now  be  considered. 

In  Fig.  116,  a  is  a  friction  wheel  keyed  to  the  shaft,  i,  of  the 
motor.  In  series  or  shunt  with  the  motor  or  its  field  is  an 
electromagnet,  g,  whose  armature,  /,  pivoted  at  d,  and  weighted 
at  e,  carries  a  shoe  or  brake,  6,  pivoted  at  c,  and  conforming  on 
its  inside  surface  to  the  circumference  of  a.  When  the  current 
passing  through  g  (and  consequently  the  motor)  ceases,  b  will 
engage  with  a  and  bring  the  latter  to  a  stop  within  a  time 


MOTORS,  RELAYS,  ETC. 


121 


proportional  to  the  relative  position  of  c.  The  disadvantage 
of  this  device  is  the  multiplicity  of  parts  and  the  waste  of 
energy  in  exciting  g. 

In  Fig.  117,  which  is  a  brake  frequently  applied  to  sema- 
phore motors,  F  is  the  field  pole  of  the  motor,  S  the  armature 
shaft,  and  P  a  pulley  keyed  to  the  latter.  B  is  a  rubber  held 
normally  against  the  face  of  P,  by  the  adjustable  spring,  H. 
B  is  carried  on  the  iron  rocking  pieces,  and  its  position  deter- 
mined by  the  adjustment,  G.  When  current  passes  through  the 
motor,  the  iron  prong  or  strip  is  attracted  to  the  tips  of  F,  and 
by  overcoming  the  tension  of  H  releases  B.  When  current 


G 


FIG. 116 


FIG. 117 


ceases,  the  cessation  of  the  flux  in  F  releases  the  prong,  caus- 
ing B  to  be  forced  against  P,  and  rapidly  overcoming  the 
inertia  of  the  armature. 

Soft  iron  disks  affixed  to  the  armature  shaft  have  also  been 
used  to  retard  the  rotation  of  the  latter.  The  disk  moves 
between  the  poles  of  a  strong  electromagnet,  and  the  reaction 
caused  by  the  setting  up  of  eddy  currents  in  this  disk  effec- 
tually brings,  the  armature  to  a  stop. 

A  motor  brake  and  the  circuit  arrangement  thereto  is  shown 
in  Fig.  118.  A  is  the  signal-control  relay  (normal  danger)  in 
series  with  the  main  battery,  common,  home  line-wire,  and 
track-relay  armature.  It  has  front  and  back  armature  con- 
tacts, C  and  B,  having  a  common  connection.  B  is  in  series 


122 


AUTOMATIC  BLOCK  SIGNALS 


with  the  motor,  so  that  the  latter  is  short-circuited  upon  itself. 
H  is  a  circuit  controller  whose  movable  contact,  E,  travels  in 
the  direction  of  the  arrow  when  the  signal  is  clearing.  When 
A,  is  energized,  a  current  passes  from  D  to  G,  Ht  motor,  and  (7. 
When  the  semaphore  is  about  cleared,  E  connects  G  and  /, 
thus  sending  a  current  through  the  brake  magnet,  J,  and  bring- 
ing the  motor  armature  to  a  stop,  current  being  cut  off  simul- 
taneously from  the  motor  circuit.  When  the  semaphore 
returns  to  danger  by  the  deenergization  of  its  slot  and  A,  the 
current  set  up  by  the  counter  e.m.f .  through  the  low  resistance 
circuit,  H-E-F-B,  produces  the  desired  retardation. 

For  a  given  output,  the  resistance  of  motors  increases  as 
the  voltage  of  the  circuits  to  which  they  are  applied  is  increased. 

lines 


FIG.  118 

In  small  motors,  the  higher  the  average  voltage  at  which  they 
operate,  the  more  efficient  do  they  become.  It  is  not  so  much 
the  actual  resistance  of  the  motor  itself  which  gives  the  increased 
efficiency,  but  the  relativity  of  this  resistance  to  the  total 
resistance,  external  to  the  motor  terminals,  such  as  that  in 
the  wiring,  relay  contacts,  batteries,  and  connections.  Hence, 
the  greater  the  operating  voltage,  the  less  will  be  the  percentage 
of  loss  in  these  subsidiary  devices,  and  the  greater  the  available 
energy  manifested  in  motor  torque. 

A  transmission  gear  for  throwing  one  or  more  semaphores  to 
clear  is  outlined  in  Fig.  119.  The  motor,  M,  drives  the  sheave, 
S,  through  the  gearing,  G.  B  is  a  brake  magnet  whose  arma- 
ture lever  when  deenergized  bears  against  the  wheel,  W,  keyed 
to  the  armature  shaft,  thus  preventing  rotation  of  the  lat- 
ter, the  adjustable  counterweight,  (7,  providing  a  time  limit. 


MOTORS,  RELAYS,  ETC. 


123 


This  arrangement  is  fastened  near  the  base  of  the  signal  pole 
and  provided  with  a  weatherproof  cover. 

Numerous  types  of  relays  are  used  in  signal  practice,  all  of 
which  embody  certain  generic  features.  Great  variations  exist, 
however,  in  the  resistance  to  which  they  are  wound,  in  one  case 
a  four-ohm  winding  being  standard,  and  in  another  a  3000-ohm 
winding  is  applied. 


M 


w 


FIG.  119 


FIG.  119o 


In  Fig.  120  a  Taylor  neutral-track  or  control  relay  is  shown. 
The  magnets,  M,  are  carried  on  the  cast  brass  base,  between  which 
and  the  sub-base  are  the  armature 
and  contacts,  the  latter  being  pro- 
tected by  a  cylindrical  glass  ring,  G. 
The  contact  fingers,  H,  are  fastened 
to  the  armature,  A,  by  lavite  bush- 
ings, L,  and  make  scraping  connec- 
tion with  the  front  contact,  F,  and 
back  contacts,  B  ;  these  being  intro- 
duced in  the  external  circuit  by  the 
binding  posts,  C.  The  coils  of  M 
are  connected  to  posts,  P. 

Fig.  121  shows  in  section  and 
elevation  a  polarized  type  glass- 
enclosed  relay  having  a  neutral  arma- 
ture, C,  and  a  polarized  armature,  G.  The  latter  swings  about  a 
pivot,  B,  the  direction  of  motion  depending  upon  the  polarity 
of  the  poles  of  magnets,  M.  A  is  a  permanently  magnetized 
rod  of  steel,  one  end  of  which  is  fastened  in  the  yoke,  H,  the 


FIG.  120 


124 


AUTOMATIC  BLOCK  SIGNALS 


other  projecting  to  the  level  of  the  pole  tips  of  M.  The  neutral 
armature  is  given  a  vertical  movement,  and  has  front  carbon 
contacts  at  D  and  back  contacts  at  E,  through  the  flexible 
strip,  F. 

The  operation  will  be  evident  from  the  plan  of  the  contact 
parts  in  Fig.  122.  When  current  in  either  direction  passes 
through  the  magnets,  the  neutral  armature,  G,  is  raised,  closing 
the  front  contacts,  D.  On  cessation  of  current,  the  back  con- 
tact only  is  closed.  If  the  pole  tip  on  the  right  hand  side  be  of 
north  polarity,  and  the  same  end  of  the  polarized  armature,  G, 


H 


be  magnetized  inductively  from  the  permanent  magnet  so 
that  it  becomes  a  south  pole,  attraction  will  result  and  the 
armature  will  turn  in  this  direction.  The  opposite  end  of  the 
armature  will  be  repelled  from  the  other  magnet  pole,  as  the  lat- 
ter is  of  south  polarity,  the  armature  end  also  being  south. 
This  causes  the  contact  fingers,  L,  to  be  forced  against  the 
carbon  contact-buttons,  K.  A  reversal  of  current  will  reverse 
these  conditions. 

Both  armatures  are  pivoted  close  to  the  field  poles,  so  that 
the  required  motion  is  slight,  hence  they  are  continually  in  a 
strong  field  when  energization  occurs,  due  allowance  being 


MOTORS,  RELAYS,  ETC. 


125 


made  for  eliminating  the  effects  of  residual  magnetism.  Adjust- 
ment is  not  required,  as  the  pivots  are  fastened  to  the  pole 
tips,  overcoming  the  variations  due  to  expansion.  The  alter- 
nate polar  contacts  are  in  multiple,  and  contact  made  with  a 
scraping  motion,  for  self-cleaning.  With  a  short  armature 
motion,  a  wide  break  results,  flexible  copper  strips  connecting 
the  binding  posts  of  the  armature  fingers. 


--K. 


j  FIG.   122 

Fig.  123  shows  a  relay  designed  for  breaking  circuits  carry- 
ing heavy  current  at  comparatively  high  potential  (for  signal 
circuits).  The  magnet  coils,  M,  are 
connected  to  the  track,  or  other  control 
circuit;  the  working  current  being  car- 
ried by  the  resilient  strip,  E,  and  carbon 
contacts,  C.  When  the  armature  falls, 
a  wide  and  rapid  break  is  introduced, 
the  back  contact  at  D  being  then  closed. 
B  is  a  series  magnetic  blow-out  coil, 
the  poles  of  its  magnetic  circuit  caus- 
ing a  powerful  flux  to  pass  across  the 
arc,  thus  rapidly  disrupting  it ;  a  slight 
movement  of  the  armature,  F,  also 
produces  a  wide  break  at  C.  The 
mechanism  is  enclosed  in  a  glass  case, 
as  the  presence  of  dust  or  insects  is  inimical  to  its  proper 
operation. 


FIG.  123 


126  AUTOMATIC  BLOCK  SIGNALS 

The  G.  E.  neutral  relay,  with  the  glass  cover  removed,  is 
shown  in  Fig.  124.  M  are  the  electromagnets,  which  actuate 
the  armature,  A.  The  latter  carries  brass  lugs  to  which  the 
carbon  contacts  C,  are  clamped,  these  making  and  breaking 
contact  with  the  flexibly  mounted  fingers,  F,  carrying  ends  Of 
silver.  The  posts,  P,  are  in  connection  with  the  terminals,  D-D. 
A  quadruple  break  is  effected  by  this  device,  which  is  very 
satisfactory.  The  contacts  cannot  be  fused  by  lightning, 
as  carbon  and  a  metal  will  not  fuse  together  in  such  cases. 


FIG.  124 

The  advantage  of  using  carbon  is  that  its  oxide  is  a  gas;  thus 
it  continually  presents  a  clean  surface,  while  the  oxide  of  silver 
itself  is  a  good  conductor. 

In  order  to  eliminate  the  false  conditions  set  up  from  relay 
contacts  being  fused  together  by  lightning,  the  relay  armature 
arrangement  shown  in  Fig.  125  is  used.  The  armature,  H, 
of  the  electromagnet,  M,  having  pole  tips,  P,  is  pivoted  at  F, 
and  carries  a  depending  member,  K,  at  the  pivot,  G.  Fastened 
to  K  is  the  spring  contact  strip,  B-E,  which  normally  is  in 
contact  with  the  connection  A.  When  B,  however,  becomes 
fused  to  the  contact  button,  C,  this  latter  point  acts  as  the 


MOTORS,  RELAYS,  ETC.  127 

pivot,  so  that  when  M  is  demagnetized  the  weight  of  H  and 

K  causes  J£  to  come  into  contact  with  D.    The  signal  magnet 

relay  or  battery  is  connected  to  D  and  C,  so  that  when  E  comes 

into  contact  with  D,  it  will  be 

short-circuited,  as   this  shunt 

has  practically  no  resistance. 

This  causes  the  signal  arm  to 

move  to  the    stop    position, 

thereby  apprising   the  main- 

tainer     that     something      is 

wrong.     Otherwise,  the  pres- 

ence  of  a  train  in  the  section 

would    not    affect    the    clear  FIG  125 

position    of   the   signal,  since 

the  release  of  the  armature  cannot  open  the  circuit  at  C-B. 

Great  care  should  be  exercised  in  selecting  the  proper  resist- 
ance value  to  which  relays  are  to  be  wound,  as  upon  this 
factor  depends  in  a  large  measure  the  life  of  the  batteries  to 
which  they  are  connected.  Thus  a  700-ohm  relay  will  take 
but  one-tenth  of  the  current  that  one  wound  to  70  ohms  would. 
Too  high  a  resistance  is  not  advisable,  as  the  wire  then  must 
be  of  very  small  diameter,  so  that  the  proper  number  of  ampere- 
turns  can  be  put  into  the  necessarily  limited  space  between 
the  cores.  Fine  wire  is  very  costly  and  difficult  to  wind,  while 
the  slightest  corrosion  or  mechanical  injury  results  in  an  open 
circuit.  Too  large  a  size  or  wire,  on  the  other  hand,  involves 
too  great  a  current  input  for  the  production  of  the  proper 
ampere-turns. 

Individual  cases  require  special  determination  of  resistance; 
so  that  no  fixed  rule  can  be  followed.  It  is  sometimes  advis- 
able to  introduce  a  German  silver  resistance  spool,  having  a 
predetermined  ohmic  factor,  in  series  with  a  relay  connected 
to  a  battery  of  too  high  voltage,  which  is  primarily  intended 
for  other  purposes.  Such  a  procedure  should  be  avoided 
whenever  possible,  however,  as  the  energy  thus  lost  in  the 
resistance  is  wasted.  Relays  in  series  must  have  resistances 
proportional  to  the  work  which  they  perform.  For  instance, 
a  relay  in  series  with  a  disk  magnet  must  have  a  low  resistance 
relative  to  that  of  the  latter,  otherwise  too  great  a  proportion 
of  the  available  energy  would  be  taken.  Relays  in  parallel 


128 


AUTOMATIC  BLOCK  SIGNALS 


must  have  high  resistance  so  that  the  changed  drop  in  poten- 
tial resulting  on  one  or  more  being  thrown  in  circuit  cannot 
materially  affect  the  others. 

Fig.  126  is  a  plotted  curve  showing  the  voltages  required 
to  operate  standard  track -relays  of  from  2  to  10  ohms  resistance. 
Curve  V  shows  the  least  voltage  that  should  be  applied  to  a 
given  relay  of  a  certain  resistance  in  practice.  This  curve 
allows  for  operation  under  favorable  conditions;  with  allowance 


.6 
.5 


I" 

*«-J 


M 


^     3     ¥     5     d    ^     a 

Resistance     in    ohms 

FIG.  126 


9      10 


for  an  average  amount  of  leakage,  due  to  the  effects  of  wet 
weather,  and  rail  proximity  to  stone  ballast. 

The  curve,  M,  shows  the  minimum  voltage  that  will  lift  the 
armature  of  the  relay  and  produce  contact  with  the  fingers. 
This  voltage  curve  allows  only  for  a  moderate  amount  of 
resistance  of  motion  due  to  friction  of  the  pivots,  and  will  not 
lift  the  armature  with  cobwebs,  interference  by  insects,  or 
other  deleterious  opposition.  On  the  other  hand,  the  presence 
of  residual  magnetism  will  require  a  lower  voltage  for  ener- 
gizing the  magnetic  circuit;  this,  however,  being  an  undesirable 
condition. 


MOTORS,  RELAYS,  ETC.  129 

There  is  a  sufficient  interim  of  current  cessation  at  the  reversal 
of  polarity  in  a  wireless  system  to  throw  the  signal  at  danger 
unless  a  slow  releasing  of  the  control  armatures  or  slots  be 
provided  for.  The  slow-releasing  slot  is  obviously  the  best 
solution  of  this  difficulty,  as  external  control  fixtures  are  then 
not  required.  The  home-slot  magnets  are  therefore  constructed 
with  a  soft  copper  tube  interposed  between  the  core  and  the 
winding,  and  equal  in  length  to  the  core.  Any  change  of  current 
in  the  latter  sets  up  strong  momentary  eddy  currents  in  the 
tube,  which  oppose  any  change  in  flux  through  the  magnetic 
circuit.  The  magnet  is  also  wound  to  sufficient  ampere-turns 
to  produce  a  much  greater  flux  than  is  actually  required,  so 


FIG.  127 

this  flux  must  die  down  a  considerable  amount  before  the 
armature  is  released.  Should  the  circuit  remain  open  after 
the  mechanical  pull  of  the  armature  becomes  less  than  the 
opposition  of  gravity  or  the  slot  arm,  the  home  semaphore 
will  return  to  danger. 

Important  adjuncts  in  a  line-wire  system  are  devices  to 
secure  adequate  lightning  protection.  They  are  particularly 
required  to  prevent  relay  points  from  fusing  together  by  afford- 
ing the  discharge  a  shunt  circuit  to  ground  of  lower  impedance 
than  by  way  of  the  former.  A  lightning  or  other  static  dis- 
charge is  in  reality  a  surging  alternating  current  of  enormous 
frequency  and  short  duration.  Such  a  discharge  will  overcome 
the  high  resistance  of  an  air-gap  rather  than  pass  around  a  few 


130 


AUTOMATIC  BLOCK  SIGNALS 


turns  of  coiled  conductor,  as  the  latter,  at  this  frequency, 
offers  an  extremely  high  inductance. 

A  bank  of  four  G.  E.  lightning  arresters  is  shown  in  Fig. 
127.  The  lines  are  connected  to  the  posts,  A,  the  instruments 
to  the  connectors,  B,  and  ground  to  the  plate,  G.  The  choke 
coils,  K,  consisting  of  a  few  turns  of  heavy  wire  in  an  insulating 
form,  are  in  series  with  the  glass  tube  enclosed  fuses,  F,  these 
latter  being  removable,  and  held  between  clips  C.  A  discharge 
will  pass  from  the  points  beneath  the  slate  end  pieces  to  the 
ground  plate  rather  than  around  the  coil.  Jumping  areas 
also  occur  between  the  lower  parts  of  the  convolutions  and  G, 
thereby  increasing  the  factor  of  safety. 

Another  common  form  of  arrester  is  illustrated  in  Fig.  128. 


FIG.  128 

Upon  a  porcelain  form  are  wound  two  connected  helices 
of  bare  wire,  D,  one  end  of  which  is  connected  to  post  A,  and 
the  other  end  to  C.  B  is  grounded,  A  connected  to  the  line 
or  track  wire,  and  C  to  the  instrument  or  wire  desired  to  be 
protected.  When  a  discharge  enters  at  A,  D  offers  such  a 
high  impedance  that  the  air-gap  between  E  and  D  is  bridged 
before  many  turns  have  carried  the  current,  thus  conveying 
it  to  the  ground.  When  a  bank  of  such  arresters  is  employed 
the  ground  plates  are  connected  by  the  strips,  F,  but  one  ground 
wire  being  used.  No  provision  is  necessary  to  prevent  ground- 
ing of  the  battery  currents,  since  they  are  of  too  low  potential 
to  bridge  this  gap,  as  would  be  the  case  on  a  commercial  light- 
ing or  power  circuit. 


CHAPTER  X. 
HALL  APPARATUS. 

THE  enclosed  disk  signal  has  a  number  of  meritorious  features, 
among  which  are  the  protection  of  the  moving  parts  against 
the  weather,  and  the  low  energy  required  to  operate  the  moving 
system.  An  electromagnet  of  comparatively 
small  size  operates  the  latter,  the  power 
required  being  insignificant  (about  2.5  watts 
in  ordinary  cases).  The  external  appearance 
of  a  post-type  normal  danger  home  and 
distant  disk-signal,  such  as  is  used  on  the 
Lehigh  Valley,  is  given  in  Fig.  129.  A  is  the 
home  banner,  which  consists  of  a  red  silk, 
cotton,  or  aluminum  disk  stretched  on  a  ring 
having  a  diameter  of  about  18  inches;  while 
B  is  the  distant  banner,  which  is  of  a  green 
fabric.  The  inside  back  of  the  housing,  C,  is 
painted  white,  so  that  when  the  disks  are  in 
the  upper  position,  the  aperture  in  the  case 
will  show  white.  The  case  is  usually  painted 
black,  so  that  the  color  of  the  opening  may 
be  seen  for  a  considerable  distance. 

Lamps   L   are  placed  in  the   rear  of   the 
apertures,  D  and  E,  before  which  spectacles 


of  the  same  color  as  the  disks  pass,  for  night 
signaling.  The  tendency  of  gravity  is  to  hold  the  disks  in  a 
position  directly  behind  the  glass-covered  apertures,  so  that 
unless  the  magnets  are  energized,  a  color  indication  will  be 
given  to  the  engineer.  Disk  signals  are  purely  color  arrange- 
ments, in  contradistinction  to  semaphore,  or  position  and  color 
signals.  Where  home  or  distant  units  on  separate  masts  are 
used,  the  banjo  is  placed  on  top  of,  and  centrally  disposed  with 
respect  to  the  pole,  which  produces  a  more  symmetrical  combi- 
nation. 

131 


132 


AUTOMATIC  BLOCK  SIGNALS 


Among  the  disadvantages  of  enclosed  signals  may  be  men- 
tioned: the  tendency  of  sleet  or  snow  to  obscure  the  disk,  by 
covering  the  glass  and  thus  giving  a  white  effect ;  the  direct  reflec- 
tion of  the  sun's  rays  in  the  engineman's  eyes,  preventing  a  clear 
view  of  the  disk ;  and  the  liability  of  the  glass  spectacles  falling 
out,  due  to  their  tendency  to  crack  from  the  effects  of  the  inertia 
of  the  moving  system.  Only  the  latter  may  be  regarded  as  a 
dangerous  feature,  since  all  railroads  require  that  a  train  stop 
when  a  signal  is  only  partially  or  imperfectly  displayed;  which, 
while  resulting  in  a  certain  loss  of  time,  has  not  argued  much 
against  their  introduction. 

Within  the  housing  or  banjo  of 
the  disk  signal  is  placed  the  arrange- 
ment shown  in  Fig.  130,  which 
constitutes  the  disk  instrument.  It 
consists  of  an  electromagnet,  F, 
whose  armature,  D,  moves  a  member, 
L,  to  which  the  banner,  B,  of  colored 
cloth  for  indications  by  day,  and 
the  disk,  A,  of  colored  glass  for  night 
indications,  are -fastened.  D  is  pivoted 
at  K,  and  its  continuity  of  motion 
causes  a  greater  flux  to  pass  through 
the  magnetic  circuit  by  decreasing 
the  sectional  area  of  the  air-gap. 
F  is  held  in  place  by  the  brass  piece 
I-E,  this  being  secured  in  the  iron 
base,  G,  by  the  eccentric  washers,  H, 
G  being  fastened  to  the  inside  of 
the  banjo.  The  external  circuit  is 
connected  to  the  binding  posts,  C. 
A  and  B  move  before  clear  glass  apertures  in  the  housing,  a 
lamp  being  placed  in  the  rear  of  A. 

This  type  of  signal  mechanism  is  used  extensively  on  the 
Lehigh  Valley,  Philadelphia  and  Reading,  and  Chicago  and 
North  Western.  The  disadvantage  of  the  cloth  banner  is  the 
rapidity  with  which  the  coloring  matter  fades  in  the  penetrating 
sunlight  which  often  strikes  it  in  both  summer  and  winter. 

An  indicator,  which  is  used  at  switches,  towers,  and  inter- 
locking points,  and  is  usually  in  series  with  the  indicator  line- 


FIG.  130 


HALL  APPARATUS 


133 


wire,  is  shown  in  Fig:  131.  It  is  in  reality  a  miniature  modifica- 
tion of  the  disk  signal  mechanism,  and  consists  of  an  armature,  C, 
pivoted  at  G,  to  which  is  attached  a  small  red  disk  or  banner,  D ; 
this  armature  moving  between  the  polar  extensions,  B,  of  an 
electromagnet,  A.  D  is  counterbalanced  by  an  adjustable  nut, 
E,  so  that  the  energy  required  to  move  the  armature  will  be  at  a 
minimum.  Insulated  from  but  fastened  to  the  magnetic  yoke  are 
the  binding  posts,  F,  to  which  the  external  circuit  is  connected. 
The  moving  system  is  of  such  design  that  the  air-gap  remains 
practically  constant,  while  its  sectional  area  continually  increases 


FIG.  131 


FIG.  132 


with  upward  movement  of  the  disk,  the  ampere-turns  required 
being  therefore  very  low.  A  slight  amount  of  rust  will  prevent 
movement  of  the  armature,  hence  the  indicator  is  enclosed  in  a 
sealed  housing  having  a  glass  aperture  before  which  the  banner 
moves. 

One  type  of  polarized  relay  is  illustrated  in  Pig.  132.  Upon 
a  porcelain  or  slate  base  the  magnet  coils,  M,  with  their  cores 
and  supports  are  mounted,  with  the  armatures,  P  and  N,  the 
former  polarized  or  permanently  magnetic,  the  latter  neutral. 
D,  D,  are  the  polar  contacts;  and  <?,  C,  the  neutral  front  and  back 
contacts,  and  fingers.  Binding  posts,  B  and  B' ,  are  for  the 
external  connection  of  these  coils  and  contacts. 


134 


AUTOMATIC  BLOCK  SIGNALS 


In  Fig.  133  an  interlocking  relay  is  shown,  in  section  and 
elevation.  This  in  reality  consists  of  two  relays,  whose  arma- 
tures, A  and  A',  are  dependent  upon  one  another.  This  is 
effected  by  the  locking  dogs,  D,  whose  points,  P,  engage  with 
the  ends,  E,  on  the  armatures,  by  the  action  of  the  rollers,  R. 
When  current  ceases  to  pass  through  the  magnet  coils,  the 
armature  falls  (if  not  locked)  and  its  roller  forces  over  the  dog, 
thereby  preventing  the  other  armature  from  dropping.  Each 


©  ©.      ©© 

©  ©      ©  © 


FIG.  133 

relay  has  four  sets  of  front  and  back  contacts,  the  construction 
being  similar  in  many  respects  to  those  herein  described. 

Fig.  134  shows  a  glass-enclosed,  also  a  glass-niounted,  neutral 
relay,  with  four  front  and  four  back  contacts.  Such  relays  are 
generally  employed  as  track  instruments,  and  are  wound  to  a 
comparatively  low  resistance. 

The  principle  of  the  type,  D,  structure  is  illustrated  in  Fig. 
135.  G  is  the  main  gear,  which,  driven  by  a  motor,  in  turn 
produces  the  reciprocation  necessary  to  clear  the  semaphore, 


HALL  APPARATUS 


135 


through  the  lever,  J.   Both  /  and  G  have  the  shaft,  A,  as  a  center, 
J  being  loose  thereon.    M  is  the  slot  magnet,  whose  armature 


FIG.  134 

is  secured  on  and  gives  motion  to  the  pivoted  bar,  F.  H  is  a 
pivot  bearing  for  the  end  of  the  rod,  B,  and  R  is  a  roller  stud 
on  the  same.  D  is  a  trigger-shaped  piece  fastened  to  G,  which 
engages  with  the  end,  E.  If  M  be  deenergized,  and  G  rotated 


136 


AUTOMATIC  BLOCK  SIGNALS 


in  the  direction  of  the  arrow  by  the  motor,  when  D  strikes  E, 
R  will  force  F  up,  and  cause  D  to  pass  E,  thus  imparting  no 
motion  to  /  or  the  semaphore,  a  stop,  S,  preventing  F  from 
being  thrown  too  far.  If  M  be  energized,  G  evidently,  by  a 
converse  reasoning,  will  cause  /  to  move  in  the  direction  of 


FIG.  135 

the  gear,  and,  clear  the  semaphore.  The  requisite  changes  in 
interconnection  and  disengagement  are  also  effected  by  the 
moving  system,  but  these  need  not  be  entered  into. 

A  type,  F,  motor  mechanism  for  a  double  semaphore  structure 
is  shown  in  Fig.  136,  and  is  similar  in  mechanical  design  to 
the  electro-gas  arrangement.  Two  independent  sets  of  mechan- 
ism are  used,  but  only  one  will  be  described.  The  motor,  15, 
frame  5,  dashpot  pistons,  and  clutch  magnets  are  supported 
by  the  iron  base,  8,  as  are  also  the  side  frames-,  6  and  7,  which 
act  as  housings  for  the  gear  shafts,  36  and  37,  and  retain  the 
clutch  levers,  11  and  12  (which  are  hidden  from  view).  Rigidly 
secured  to  the  dashpot  cylinder,  29,  is  the  thrust  rod,  13,  the  dash- 
pot  pistons  being  mounted  on  pedestals  within  the  frame  and  on 
the  base,  8.  This  thrust  rod  is  guided  by  the  cylinder,  29,  the 
upper  end  of  13  passing  through  a  bearing  in  frame  5.  The  sema- 
phore, connected  to  24  by  a  link,  is  held  at  clear  by  a  latch  en- 
gaging with  a  lug  on  the  clearing  lever,  22.  The  thrust  rod,  13, 
carries  the  latch  support,  96,  which  in  turn  carries  clearing  lever 


HALL  APPARATUS 


1ST 


22,  thrust  piece  100,  and  a  latch  engaging  with  the  lug  on  1,  to 
hold  the  semaphore  at  clear.  100  carries  a  V-shaped  latch, 
33,  which  engages  with  the  lug  on  the  clearing  lever,  22,  the 
clearing  operation  being  indirectly  performed  by  the  train  of 
motor-driven  gears,  3. 
The  movable  contacts  of  the  circuit  controller,  21,  are  operated 


FIG.  136 

by  the  control  rod,  49,  and  escapement  lever,  47;  the  latter  is 
thrown  by  the  latch  support  roller,  52.  The  front  armatures 
of  the  clutch  magnets,  1  (one  magnet  being  on  each  side),  con- 
trol the  parallel  contacts  of  the  motor  circuit,  while  the  back 
armatures  are  secured  to  the  clutch  levers,  11,  thus  keeping 
the  latter  under  the  control  of  the  magnets.  When  the  home 
blade  is  at  stop,  the  controller  contacts  for  the  series  motor, 
15,  are  closed,  and  the  distant  clutch  magnets  are  on  open 


138  AUTOMATIC  BLOCK  SIGNALS 

circuit,  so  that  the  latter  cannot  be  cleared  before  the  home  is 
fully  at  clear.  The  motor  circuit  is  closed  directly  the  home 
clutch  magnet  is  energized,  by  the  front  contacts,  4;  while 
simultaneously  the  rear  armature,  9,  is  attracted,  thus  pre- 
venting the  clutch  lever,  11,  from  moving  when  the  stud  roller 
exerts  its  pressure.  The  motor  now  drives  the  gears  and 
brings  38  under  100,  forcing  it  up.  As  11  is  securely  held  by 
9,  22  cannot  swing  back ;  hence  the  thrust  rod  and  all  its  appur- 
tenances are  carried  to  the  clear  position,  in  moving  to  which 
roller,  19,  pivoted  in  22,  rolls  against  11.  The  final  portion  of 
this  movement  to  clear  brings  roller  52  against  the  short  link 
of  escapement,  47,  rocking  it  about  56,  so  that  rod  49  operates 
the  circuit  controller  and  opens  the  motor  circuit,  at  the  same 
time  closing  that  of  the  distant.  The  home  is  held  at  clear 
by  the  action  of  the  lug  on  11,  which  engages  with  a  latch  on 
96,  releasing  the  downward  pressure  on  the  stud  roller,  and 
allowing  the  distant  to  be  cleared  by  the  motor.  A  stud  roller 
similar  to  38  is  on  the  opposite  side  of  the  gear  and  displaced 
180°  from  38;  for  clearing  the  other  blade,  a  similar  structure 
to  96-100-52-,  etc.,  is  employed. 

After  having  been  cleared,  38  moves  beneath  100,  the  signal 
circuit  being  broken  as  soon  as  the  clutch  magnet  is  energized, 
as  before.  The  motor  circuit  is  opened  by  the  front  armature, 
and  the  rear  armature  allows  11  to  swing  back  sufficiently  to 
permit  the  retaining  latch  to  disengage  and  cause  the  return 
to  danger  by  gravity,  this  movement  being  dampened  by  the 
dashpot,  29.  As  soon  as  this  movement  begins,  the  circuit 
controllers,  21,  are  reversed,  and  should  the  motor  inadver- 
tently become  on  closed  circuit  the  gears  will  merely  revolve 
uselessly,  since  38;  cannot  clear  the  semaphores  unless  clutch 
magnets,  1,  are  energized.  Should  the  clutch  magnets  become 
deenergized  with  the  blades  partly  at  clear,  22  would  swing 
back,  since  latch  33  is  permitted  to  pass  the  clearing  lever  lug, 
thereby  throwing  the  semaphore  to  danger,  as  100  swings  on 
its  pivot  105  to  the  normal  position  after  the  stud  roller  has 
moved  beneath  it. 

A  double  electromechanical  slot  is  shown  in  elevation  and 
section  in  Fig.  137.  The  dashpot  shells,  Z),  are  secured  to  the 
rods,  R,  which  are  interposed  in  the  semaphore  links.  When  B 
is  forced  upward  by  the  operator's  lever,  L  will  tend  to  swing 


HALL  APPARATUS 


139 


outward  on  its  pivot.  If  the  enclosed  coil  magnet,  M,  be  ener- 
gized, its  armature,  A,  will  hold  C  at  the  inner  position,  so  that 
L  cannot  move,  and  motion  of  B  is  transmitted  to  R.  If, 
however,  M  be  deenergized,  roller  0  throws  C  over,  in  opposition 


FIG.  137 

to  the  spring  S,  and  B  moves  upward  without  throwing  the 
semaphore. 

In  Fig.  138,  which  illustrates  a  combined  tower  indicator  and 
bell,  S  is  a  miniature  semaphore  showing  the  condition  of  a  track 
section  or  signal,  which  is  thrown  by  the  armature,  A,  of  the 
magnet,  M ,  through  the  bell  crank,  L.  When  S  moves  to  dan- 


140 


AUTOMATIC  BLOCK  SIGNALS 


ger,  the  clapper  C,  on  the  semaphore  rock-shaft  strikes  a  gong,  G, 
thus  warning  the  signal  operator.  The  armature  also  carries  front 
and  back  contacts  T  for  introduction  in  the  circuits  of  the  tower. 


Fig.  139  outlines  a  switch  instrument  which  does  not  close 
the  circuit  contacts  (on  a  normal  danger  network)  until  the 
rail  point  has  reached  its  fully  normal  position.  These  contacts, 
C,  are  actuated  by  the  links,  L,  arranged  about  the  rock  shaft,  R. 
When  the  sector,  S,  is  moved  in  the  direction  of  the  arrow,  the 


FIG.  139 

steel  block,  B,  engages  with  the  piece,  A,  and  thus  opens  the  con- 
tacts.   The  switch  link  is  fastened  to  D. 

A  standard  switch  indicator  is  shown  in  >Fig.  140,  the  miniature 
semaphore  being  moved  in  a  somewhat  similar  manner  to  that 


HALL  APPARATUS 


141 


shown  in  Fig.  138.  Front  and  back  contacts  are  also  provided, 
a  push  button,  P,  being  introduced  in  series  with  the  magnet 
winding,  and  in  shunt  with  the  front  "stick"  contact.  With 


FIG.  140 


this  device,  a  trainman,  by  pressing  the  button,  may  ascertain 
the  condition  of  the  two  preceding  blocks,  the  semaphore  being 
normally  in  the  danger  position. 

In  Fig.  141  the  standard  wireless  connections  for  single-track 


FIG.  141 

one-way  movements  with  overlap  appear.  The  motor,  Af,  is 
in  series  with  the  front-contact  of  a  slow-releasing  relay  in  series 
with  the  track  relay,  D,  front  contact,  the  contacts,  1,  2,  3,  4 
being  operated  simultaneously  by  movement  of  H. 


142 


AUTOMATIC  BLOCK  SIGNALS 


In  Fig.  142  the  wireless  connections  of  a  normal  clear  home 
and  distant  signal,  S,  for  one  of  the  tracks  of  a  double-track  road, 
and  a  polarized  relay,  P,  are  shown.  The  scheme  of  interconnec- 
tion is  an  elaboration  of  that  already  given  in  Fig.  70,  utilizing 
a  compound  slot,  h,  in  series  with  the  motor  for  the  home  blade 
and  a  simple  wound  slow-releasing  slot,  d,  for  the  distant.  This 
is  the  usual  practice,  as  the  home  is  cleared  first,  and  the  effect 


FIG.  142 

of  drop  in  potential  is  not  so  manifest  in  the  case  of  the  distant 
slot.  E  is  a  polarity  reverser,  for  the  control  of  the  preceding 
distant. 

Fig.  142a  shows  the  standard  connections  for  a  normal  clear 
home  and  distant  disk-signal  on  one  of  the  tracks  of  a  double- 
track  road,  H  being  the  home  banjo.  This  arrangement  is 
an  extension  of  the  home  banjo-circuit  given  in  the  preceding 
chapter,  a  polarized  relay  being  used,  as  in  the  latter  case. 


HALL  APPARATUS 


143 


T  has  two  components,  which  are  connected  in  series.  When 
one  of  the  neutral  armatures  comes  in  contact  with  the  back 
contact  point  (by  short-circuiting  of  the  track)  but  one  cell 
is  connected  to  the  latter.  N  operates  both  blades,  being 
under  rather  heavy  discharge  when  the  low-resistance  winding 
is  in  circuit  and  the  disk  being  cleared,  and  under  slight  demand 
when  at  clear.  The  insulating  joints  are  not  shown  opposite, 


FIG.  142o 

as  in  practice  they  are  staggered,  in  common  with  the  ordinary 
joints. 

Figs.  143  and  143a  are  consecutive  circuits  showing  the  Hewett 
line-wire  scheme  of  normal  danger  operation,  with  a  normally 
open  track- circuit,  the  track  relays  being  normally  closed  for 
switch  indicator  control.  At  signal  522,  the  track  element  is 
connected  in  series  with  the  opposed  or  differential  relays  or 
windings  A  and  B  (having  a  common  armature),  but  in  this  case 


144 


AUTOMATIC  BLOCK  SIGNALS 


HALL  APPARATUS 


145 


no  energization  results,  so  contact  C  is  open.    When  A  (which  is 
in  shunt  with  the  track)  is  short-circuited  by  a  train  or  otherwise 


B  is  fully  energized,  and  consequently,  C  is  raised ;  T  receives 
current  from  K,  and  is  in  series  with  a  differential  winding,  U. 

At  532,  a  train  appears  in  the  home  block,  which  short-circuits 
the  upper  winding,  L,  and  fully  energizes  M ;  thus  raising  both 


146  AUTOMATIC  BLOCK  SIGNALS 

contact  points,  and  clearing  542.  The  4-ohm  relay,  0,  is  also 
energized  (by  the  closing  of  the  lower  contact  of  M)  from  P. 
The  home  mechanism,  when  cleared,  closes  two  contacts  and 
opens  one ;  when  moving  to  stop,  the  reverse ;  D  is  a  relay  having 
two  connections  of  its  windings:  one  of  200  ohms,  the  high 
resistance,  and  the  other  of  20  ohms,  this  being  effected  by  a 
shunting  contact  operated  by  the  home  mechanism.  Also, 
when  either  the  home  or  distant  clears,  short-circuiting  con- 
tacts are  operated,  which  throw  into  circuit  the  high-resistance 
slot  or  retaining  coil,  which  maintains  the  clear  position  of  the 
semaphores,  with  insignificant  current  consumption. 

When  the  armature  contact,  Q,  is  closed,  7  is  connected  to  the 
track;  and,  if  energized,  the  local  home  will  clear,  and  subse- 
quently, the  distant.  At  522,  N  is  a  resistance  in  series  with  the 
distant  signal  line  through  G,  which  is  the  cause  of  a  supple- 
mental energization  of  /,  having  a  subsidiary  control  over  7. 
The  indicator,  R,  is  connected  to  the  indicator  line  and  common, 
and  is  in  series  with  F.  The  home  semaphore  at  522  is  con- 
trolled by  E,  and  at  532  by  a  front  contact  of  7. 


CHAPTER  XI. 
UNION    APPARATUS. 

IN  Fig.  144  the  track  and  motor  connections  embodied  in  the 
Union  standard  normal  clear  polarized  rail- circuit  scheme  of 
operation  are  shown.  The  home  signal,  H,  protects  the  block 
immediately  behind  it  (not  shown),  the  approaching  train  in 


Mam  botfery 


U 


•S/o* 
re/eas/n<? 


Tr-oc/t  6o#eiy 
fb/e 


Trotn 


V 


FIG.  144 


the  block  preceding  short-circuiting  the  track  section  and  hold- 
ing the  signal  at  D  at  stop,  in  a  manner  now  to  be  described. 
Excepting  the  track  battery  and  pole  changer  at  H,  the  entire 
arrangement  of  accessories  and  connections  shown  in  the  figure 
is  at  D.  H  has  the  same  subsidiary  devices,  but  their  delineation 
would  over-complicate  the  diagram. 

The  track  battery  at  H  is  not  connected  directly  to  the  track, 
a  pole  changer  being  introduced.  The  polarized  relay  is  con- 
nected at  the  other  end  of  the  block  (relay  control  being  inter- 
posed where  the  blocks  are  of  excessive  length)  and  is  affected 

147 


148  AUTOMATIC  BLOCK  SIGNALS 

by  three  conditions:  (1)  the  cessation  or  continuance  of  current, 
irrespective  of  its  polarity;  (2)  the  establishing  of  current  of  one 
polarity;  and  (3)  establishing  of  current  of  the  opposite  polarity. 
Under  certain  conditions  it  would  be  apparent  that  the  polar 
contact  would  still  remain  closed  upon  cessation  of  current,  when 
the  latter  was  in  the  proper  direction.  To  provide  against  such 
a  contingency,  a  supplemental  break  is  introduced,  as  will  be 
apparent  later. 

The  polarized  relay  has  two  armatures,  a  neutral  and  a  polar; 
the  former  being  raised  whenever  current  circulates  around  the 
coils ;  and  the  latter  closing  its  contact  when  the  current  is  in  one 
direction  and  opening  it  when  a  reverse  polarity  is  set  up.  The 
neutral  contact  controls  the  home  semaphore,  and  the  polar 
contact  the  distant  semaphore  in  every  case.  When  a  train 
occupies  the  block  (as  is  the  case  for  the  signal  at  D,  or  by  rea- 
son of  an  open  switch  or  similar  cause),  the  polarized  relay  is 
de-energized;  the  home  signal  assuming  the  danger  position,  by 
the  action  of  gravity.  This  movement  to  stop  operates  the 
pole  changer,  and  thereby  throws  the  distant  signal  in  the  rear 
to  the  caution  position,  through  the  action  of  the  polar  con- 
tact, distant  slot,  and  gravity. 

The  reversal  of  polarity  must  evidently  cause  a  momentary 
drop  of  the  neutral  armature,  due  to  the  instantaneous  ces- 
sation of  current  through  the  magnet  coils,  followed  immediately 
by  a  sweeping  out  of  the  residual  flux.  As  the  contact  of  this 
armature  is  in  the  home  slot  and  motor  circuits,  it  follows 
that  the  signal  arm  must  move  to  danger.  However,  an 
intermediate  slow-releasing  relay  contact  is  in  series  with 
the  motor  and  home  slot,  the  magnets  of  this  relay  being  in 
series  with  the  neutral  armature  contact  and  having  a  very 
high  self-induction,  being  also  provided  with  a  copper  tube 
for  choking  effect,  so  that  before  the  self-induction  current 
occasioned  on  breaking  the  circuit  can  neutralize  itself  (and 
consequently  the  residual  flux  cease)  the  circuit  is  again  com- 
pleted, and  its  magnetism  fully  restored;  the  home  signal  arm 
being  thus  unaffected. 

The  slot  magnets  are  compound  wound,  having  two  sepa- 
rate windings,  the  inner  of  many  turns  and  high  resistance 
and  the  outer  of  few  turns  and  low  resistance.  The  high- 
resistance  coils  are  connected  in  multiple  with  the  main  battery, 


UNION  APPARATUS  149 

and  the  low- resistance  coils  in  series  with  the  motor;  so  that 
when  a  heavy  current  passes  through  the  motor  it  must  pro- 
duce a  corresponding  increase  in  the  magnetic  effect  upon  the 
slot  magnet  armatures. 

The  sets  of  contacts,  1,  2,  and  3,  are  indirectly  operated  by 
movement  of  the  home  semaphore;  and  4  by  the  distant. 
Both  2  and  3  are  normally  closed  (when  the  signal  is  at  clear), 
while  1  is  normally  open  (shown  closed  in  the  figure,  since 
the  signal  is  at  stop).  When  the  distant  arm  is  at  clear,  4  is 
opened;  when  at  caution,  closed,  as  in  the  diagram.  The 
high-resistance  home  slot  winding  is  connected  across  the  bat- 
tery through  the  contact  of  the  slow-releasing  relay;  the 
same  winding  of  the  distant  slot  being  in  multiple  with  the 
battery,  through  the  polar  and  neutral  contacts  of  the  polar- 
ized relay  on  one  side,  and  through  the  home  operated  con- 
tacts 3  on  the  other  side. 

The  motor  is  connected  to  the  battery  for  the  movement 
of  the  home  blade  through  the  low-resistance  winding  of  the 
home  slot,  normally  open  contacts  1,  and  the  slow-releasing 
relay  armature;  and  for  movement  of  the  distant  semaphore 
through  the  normally  closed  contacts  2,  normally  open  con- 
tacts 4,  low-resistance  winding  of  the  distant  slot,  and  the  polar 
and  neutral  contacts  of  the  polarized  relay. 

A  partial  elevation  and  section  of  one  type  of  such  a  signal 
mechanism  for  semaphores  is  shown  in  Fig.  145.  The  motor, 
17,  through  its  armature  shaft,  39,  drives  the  large  gear,  21, 
whose  pinion,  22,  engages  with  the  sprocket-carrying,  gear  20. 
The  home  semaphore  is  connected  to  the  rod,  7,  pivoted  at  33, 
and  the  distant  to  8;  the  former  being  at  clear.  Motion  is 
imparted  to  these  rods  by  the  movable  members,  37,  which 
rock  about  a  shaft,  32.  These  members  carry  the  slot  magnets 
9  and  34,  to  which  connection  is  made  through  flexible  cable, 
to  the  binding  posts,  36.  The  armatures,  40,  of  these  magnets, 
through  the  latch  ends,  31,  engage  with  the  train  of  links,  30, 
25,  29,  and  28,  so  that  when  34  is  energized  under  specific 
conditions,  the  cam  piece,  28,  is  immovable.  , 

To  the  ends  of  the  arms,  37,  are  pivoted  two  links,  6  and  10. 
The  former  operates  the  plunger,  4,  of  a  dashpot,  the  shell,  3,  of 
which  is  held  in  the  mechanism  frame.  The  relative  retarda- 
tion is  varied  by  the  screw,  2,  which  governs  the  discharge  of 


150 


AUTOMATIC  BLOCK  SIGNALS 


the  entrained  air  through  the  orifice,  1.  These  dashpots  prevent 
spasmodic  movements  of  the  mechanism  when  returning  to 
the  stop  position  by  gravity.  Link  10  operates  a  current 
reverser  or  pole  changer,  the  essential  parts  of  which  are  the 
sets  of  contact  springs,  14  and  13,  with  the  scraping  pieces,  12. 
Connection  to  the  track  circuit  is  effected  through  the  binding 
posts,  11,  15,  and  42. 


FIG.  145 


As  only  the  home  blade  is  at  the  clear  position,  the  distant 
block  must  be  occupied  or  dangerous.  If  it  be  supposed  to  be 
again  clear,  9  will  be  energized  simultaneously  with  the  passing 
of  the  current  through  the  motor.  As  the  motor  gains  speed, 
the  chain  starts  to  move,  and  as  44  is  held  rigid  by  the  inter- 
posed links  and  the  spring,  38,  37  will  be  carried  upward  by 
the  action  of  the  roller  engaging  with  44.  When  it  reaches 
its  extreme  upward  position,  a  stud  opposes  gravity  through 


UNION  APPARATUS 


151 


the  latch,  41,  latching  taking  place  when  40  passes  the  hook.  At 
the  same  time,  the  motor  circuit  is  opened  at  contact  springs, 
26,  by  the  insulated  strip,  27,  through  the  pivoted  piece,  46, 
which  37  strikes,  since  43  and  24  are  in  series  with  the  motor. 
The  brake,  45,  is  applied  when  the  current  through  the  motor 
ceases,  thus  bringing  the  armature  to  an  almost  immediate 
stop.  The  electrical  connections  have  been  described  in  con- 
nection with  the  preceding  figure,  the  external  and  intercon- 
nections being  made  at  the  posts,  5. 

In  Fig.  146  the  arrangement,  which  is  frequently  used  to 
clear  the  signal  arm,  is  isolated.  The  motor  drives  the  chain, 
J,  in  the  direction  of  the  arrows.  This  causes  a  roller,  R,  to 
strike  the  pivoted  member,  Ey  which  is  connected  to  the  links, 
F  and  G.  The  semaphore  rod  is  pivoted  at  A,  and  the  whole 


FIG.  146 

structure  at  J5,  the  dashpot  plunger  and  polarity  changer  being 
operated  from  end  I.  If  the  slot  magnet,  D,  be  energized,  arma- 
ture C,  through  its  hook  end,  will  prevent  H  from  moving 
when  E  is  struck,  through  the  action  of  F  and  G.  Hence  R 
raises  E  and  the  entire  arm  about  B  as  a  center,  thus  clearing 
the  semaphore  in  opposition  to  gravity.  If  D  is  not  energized, 
this  cannot  occur;  and  if  it  be  de-energized  when  the  blade  is 
at  clear,  the  release  of  H  will  cause  it  to  fall  to  stop. 

The  Union  standard  disk  mechanism  is  illustrated  in  Fig. 
147.  It  consists  of  an  aluminum  disk  or  colored  banner,  D, 
carrying  a  lens  at  its  center;  and  suspended  upon  a  rod,  which 
passes  through  the  pivoted  armature,  A,  of  the  electromagnet, 
M.  The  moving  system  is  counterweighted  at  W,  the  electro- 
magnet being  held  within  a  box  fastened  to  the  rear  of  the 
narrow  case,  a  front  view  of  which  is  shown  at  C.  A  hinged 


152  AUTOMATIC  BLOCK  SIGNALS 

lamp  is  placed  in  the  rear  of  C  for  night  signaling,  the  rays  of 
this  lamp  passing  through  a  lens  at  the  center  of  the  disk. 
The  rear  of  the  aperture,  P,  before  which  the  banner  moves, 
is  painted  white,  so  that  when  the  latter  is  raised  a  clear  indi- 
cation is  given,  the  lower  end  only  being  visible,  the  clear 
lens  before  the  lamp  being  also  seen  at  the  center  of  P.  An 
opening  is  provided  so  that  repairs  and  connections  can  be 
readily  made. 

In  Fig.  148  a  slow  releasing  relay  is  shown,  A  being  the 
armature,  B  the  back  contact  prong,  and  F  the  front  contact. 
The  magnets  are  wound  to  such  a  resistance  that  a  high  self- 
induction  results  at  the  current  strength  normally  passing 


FIG.  147 

through  the  coils.  The  magnetic  circuit  is  long  and  of  generous 
sectional  area,  the  pole  tips  presenting  a  large  surface  to  the 
armature.  A  soft  copper  sleeve  is  slipped  over  each  core 
before  the  winding  is  put  on.  The  eddy  currents  set  up  momen- 
tarily in  the  sleeve  when  any  change  in  exciting  current  occurs, 
oppose  any  change  in  flux,  and  thus  tend  to  retain  the  mag- 
netism. These  factors,  combined  with  a  short  lift,  small  air 
gap,  large  percentage  of  residual  magnetism,  and  high  working 
flux  density  (much  greater  than  is  actually  required  for  the 
mechanical  work  done)  produce  a  slow  release  of  the  armature 
when  the  energizing  current  is  interrupted.  Such  a  relay  is 
used  in  connection  with  the  polarized  wireless  system,  when 
slow-releasing  slots  are  not  employed,  to  prevent  open-circuiting 


UNION  APPARATUS 


153 


of  the  home  slot  circuit  when  a  momentary  reversal  of  polarity 
occurs  at  the  polarized  relay. 

Fig.  149  illustrates  a  vertical  rotary  switch-circuit  controller 
in  section.  This  instrument  is  intended  to  short-circuit  the 
track  relay  at  a  track  switch  when  the  latter  is  open,  or  to 
short-circuit  the  signal  relay.  When  the  switch  is  closed, 
the  contacts  are  open,  so  that  the  electrical  conditions  of  the 
section  are  not  interfered  with.  The  arrangement  consists  of 
the  dust  and  waterproof  cast  iron  housing,  A,  provided  with  a 


FIG.  148 


FIG.  149 


hinged  cover,  B,  which  is  held  securely  in  place  when  closed 
by  a  lock  and  clasp,  C.  Fastened  to  an  insulating  strip  are 
the  phosphor-bronze  platinum-tipped  strips,  F,  with  the  binding 
nuts,  D,  for  connection  to  the  external  circuits.  The  housing 
is  fastened  to  the  long  tie,  /,  by  lag  screws,  adjacent  to  the 
switch-point  rail.  It  is  connected  to  the  latter  by  the  rod,  7, 
which  imparts  motion  to  the  crank,  G,  fastened  to  the  cam 
piece,  H,  the  pivot  being  the  shaft,  N.  Riding  on  the  inclined 
flat  lip,  H,  is  a  small  roller,  L,  fastened  to  a  cast  iron  rocking 
piece  pivoted  to  the  shaft,  M,  L  being  pressed  against  H  by 
the  action  of  the  spring,  0. 


154 


AUTOMATIC  BLOCK  SIGNALS 


Closing  the  switch  will,  through  the  rod,  7,  produce  a  move- 
ment of  the  rotary  cam  piece  and  thus  throw  the  roller,  L}  up- 
ward, which  compresses  the  spring,  0,  and  moves  the  lower  insu- 
lating strip  downward,  allowing  the  contact  strips,  F,  to  separate, 
thus  breaking  the  circuit.    With  G  in  the  position  shown  in 
the  figure,  the  switch  is  open,  the  contact  strips  thus  short- 
circuiting  the  track.    The  pur- 
pose of    the    rotary  cam  is  to 
absorb  the  motion    given  to  G 
,       by  every  car  wheel  which  passes 
I     over  the  switch-point  rail,  and 
prevent  its  being  communicated 
f     to  the  contact  strips.     In  Fig. 
150    the    mode    of    application 
of   such  a  box  to   a   switch   is 
shown.      K  is  the  switch-point 
rail,  which  is  connected  to  the  box  crank  by  the  rod,  7. 
In  Fig.  151  a  duplex  rotary  circuit-controller  is  illustrated. 


FIG.  150 


FIG.  151 


This  arrangement  is  intended  to  control  from  one  to  four  sep- 
arate circuits;  or  it  may  be  employed  to  reverse  the  polarity 
or  connections  of  two  independent  circuits.  It  is  frequently 
employed  in  place  of  the  switch  circuit-controller  above  described. 
The  instrument  consists  (Fig.  151a)  of  two  operating  cams,  V, 


UNION  APPARATUS 


155 


whose  outer  edges  bear  against  rollers  arranged  on  pivoted 
bars,  the  latter  carrying  contact  springs  and  connectors,  X. 

Within  the  weatherproof  cast  iron  housing,  11  (this  being 
merely  a  connection  plan),  are 
two  cams,  14  and  27,  arranged 
to  move  about  a  pivot,  26. 
These  cams  are  secured  to  the 
crank,  25,  operated  by  the  switch, 
semaphore,  or  interlocking  ma- 
chine rod,  24.  The  outer  edges 
of  the  cams  bear  against  small 
rollers,  13,  secured  to  the  rocking 
members,  12,  pivoted  at  28. 
These  rocking  members  carry 
the  insulated  contact  springs, 
21,  22,  17,  and  18. 

The  stationary  pieces,  15  and 
29,  also  carry  insulated  contact 
spring  strips,  16,  19,  20,  and  23, 
which  are  in  or  out  of  contact 
with  the  movable  strips  accord- 
ing to  the  position  of  the  cams, 
and  consequently  the  position 
of  24.  Connecting  posts,  30 

and  31,  to  which  the  wires,  5  and  6  pass,  are  insulated  and 
stationary,  and  have  a  projection  beneath  which  obstructs 
the  motion  of  the  movable  contact  springs.  In  the  position 
of  the  cams  shown,  21  is  in  contact  with  30,  and  31 
with  17. 

To  sho,v  the  use  of  the  arrangement  as  a  reverser  of  polarity, 
suppose  that  a  track  battery  is  connected  to  1  and  2,  one  track 
rail  being  connected  to  3  and  4.  If  the  other  rail  is  connected  to 
5,  it  is  evident  that  the  polarity  of  the  track  circuit  is  reversed 
at  every  consecutive  movement  of  24;  which  may  be  secured  to 
the  home  semaphore  of  a  signal  on  the  wireless  or  polarized 
track-circuit  system.  By  connecting  one  side  of  one  circuit  to 
1  and  3,  and  the  other  side  to  7  and  8,  we  have  double-pole 
simultaneous  control  of  two  circuits.  Numerous  such  combi- 
nations will  occur  to  the  signalman. 

Fig.  152   shows  a   polarized  indicator   mechanism,  such   as 


FIG.  151a 


156 


AUTOMATIC  BLOCK  SIGNALS 


is  used  at  a  siding  or  crossover,  or  to  indicate  the  state  of  two 
or  more  distant  devices  having  suitable  battery  connections. 
When  applied  at  a  siding  switch,  it  apprises  the  brakeman  of 
an  approaching  train,  and  the  movement  of  the  home  signal 
governing  the  section  in  which  the  switch  is  located.  When 
used  in  conjunction  with  a  slotted  mechanical  signal,  it  may 
similarly  indicate  the  approach  of  a  train,  and  the  clearing  or 
return  of  the  semaphore. 


FIG.  152 

It  consists  of  an  electromagnet,  M,  whose  permanently  mag- 
netized armature,  A,  is  held  centrally  in  a  state  of  static  equi- 
librium by  the  adjustable  springs,  S,  between  the  pole  pieces,  R. 
This  armature  is  pivoted  at  P,  and  engages  at  its  lower  end  with 
a  rocking  member,  B,  the  latter  giving  motion  to  a  pointer  (not 
shown)  which  has  three  positions  of  rest,  according  to  the  direc- 
tion of  the  current  or  its  continuity.  The  mechanism  is  enclosed 
in  a  cast  iron  box,  placed  at  the  top  of  an  upright  located  near 
the  switch. 


UNION  APPARATUS 


157 


Fig.  153  shows  a  front  and  side  elevation  of  a  multiple  unit 
semaphore  indicator,  with  the  binding  posts  and  armature  con- 
tacts. This  type  has  three  front  contacts,  1,  2,  and  3,  also  two 
back  contacts,  4  and  5.  The  electromagnet,  8,  through  the 
armature,  11,  operates  a  shaft,  7,  which  is  secured  to  a  miniature 
semaphore  moving  before  the  face  glass,  9.  Interconnection 
and  connection  to  external  circuits  is  effected  at  the  binding 
posts,  10.  These  instruments  are  mounted  in  a  moisture-proof 


FIG.  153 

housing  in  gangs  or  banks,  and  find  application  in  train  sheds, 
signal  towers,  and  stations.  Frequently  single-stroke  and  vibrat- 
ing bells  supplement  these  devices,  giving  an  audible  announce- 
ment of  the  semaphore  movement.  A  common  bell  for  each 
bank  may  be  used,  but  it  is  better  practice  to  employ  individual 
bells. 

Fig.  154  illustrates  a  neutral  type  disk  indicator,  which  is 
applied  where  it  is  desired  that  two  indications  be  given,  as,  for 
example,  to  indicate  the  condition  of  a  given  block,  whether 
occupied  or  clear.  It  consists  of  a  metal  disk,  D  (usually  red), 


158 


AUTOMATIC  BLOCK  SIGNALS 


which  is  actuated  by  the  armature  of  the  electromagnet,  M, 
the  latter  being  in  series  with  a  track-relay  armature  contact. 
D  is  fastened  upon  the  vertical  shaft,  S,  which  is  fastened  by  a 
link  and  stud,  P,  to  an  extension,  E,  of  the  armature.  When  M 
is  energized,  E  moves  outward  a  trifle,  thus  permitting  P  to 
swing  around,  and  present  the  edge  of  the  disk  to  the  observer. 
B  is  of  non-magnetic  material,  the  armature  being  partly  enclosed 
by  it. 


FIG.  154 


FIG.  155 


To  apprise  a  tower  attendant  of  the  presence  of  a  train  in  a 
certain  block,  or  indicate  the  approach  of  a  train  to  a  signal, 
a  drop  annunciator  is  used.  This  consists,  as  shown  in  Fig.  155, 
of  a  banner,  #,  with  the  desired  inscription  on  its  face,  which 
moves  before  a  glass-covered  aperture  in  the  housing  (shown 
removed).  This  banner  is  affixed  to  a  pivoted  casting,  L,  which 
is  provided  with  a  handle  or  finger,  H,  and  is  held  in  its  upward 
position  by  a  trip  upon  the  piece,  S,  pivoted  at  P,  whose  position 
and  movement  are  adjustable.  To  the  latter,  the  armature,  A, 
of  the  electromagnet,  M,  is  fastened.  When  a  current  passes 


UNION  APPARATUS 


159 


through  M,  B  is  released  in  an  obvious  manner,  and  is  restored 
by  means  of  the  handle,  H.  An  auxiliary  circuit  for  audible 
announcement  of  the  movement  of  B  is  sometimes  made  use  of, 
and  consists  of  a  battery  and  bell  in  series  with  the  contacts, 
K-C,  the  latter  being  closed  when  L  is  in  its  lower  position. 

Drop  annunciators  are  used  in  connection  with  crossing  cir- 
cuits (see  Fig.  31)  to  announce  approaching  trains,  and  at  inter- 
locking towers  to  avoid  delays  caused  by  switching  engines 
drilling  within  yard  limits.  Delays  to  through  passenger  trains 
by  long,  slow-moving  freight  trains,  which  receive  a  signal  prior 
to  the  former,  are  prevented  by  its  use,  so  that  the  operator  can 
first  give  the  passenger  train  the  right  of  way. 


FIG.  156 

One  form  of  circuit  controller,  the  application  of  which  was 
considered  in  Fig.  77,  is  illustrated  in  Fig.  156,  G  being  a  part 
section  and  elevation,  and  F  a  front  view.  The  electromagnet, 
A,  enclosed  in  a  box  having  a  glass  door,  H,  is  in  series  with  the 
armature  contacts,  D-C,  connection  to  external  circuits  being 
afforded  by  the  lugs,  E.  When  the  knob,  B,  is  raised,  these  con- 
tacts are  .closed,  hence  a  current  passes  around  A  (providing 
the  external  circuit  is  otherwise  complete)  thus  raising  the 
armature,  C,  and  maintaining  the  energization  of  A.  Should 
the  external  circuit  be  opened,  C  will  fall,  and  A  will  be  dee'n- 
ergized,  until  C  is  again  raised  by  the  operator,  irrespective  of 
the  condition  of  the  external  circuit. 


CHAPTER  XII. 


ELECTRO-PNEUMATIC  AND  ELECTRO-GAS  SYSTEMS. 

ELECTRO-PNEUMATIC  systems,  which  are  used  on  many  busy 
lines,  employ  low  voltage  controlling  circuits,  the  working 
medium  for  operating  switches  and  semaphores  being  com- 
pressed air,  supplied  by  a  local  compression  plant  and  conveyed 
to  the  subsidiary  apparatus  through  underground  pipes.  The 
circuits  generally  used  on  such  systems  (normal  clear  for  single 
track)  are  shown  in  Fig.  157. 


1 

U 

i— 

n 

»   • 

•  i 

I 

u, 

~~n. 

•^ 

-n* 

1 

3' 

—  3. 
Jfi 

TCTf 


123 

FIG.  157 


Three  consecutive  home  and  distant  signals,  121,  123,  and 
125,  are  considered,  with  single  sections,  a  train  being  on  the 
block  protected  by  125.  The  admission  of  air  to  the  cylinder 
operating  the  home  semaphore  is  controlled  by  the  electro- 
magnet, H,  and  to  the  distant  cylinder  by  D.  A  circuit  con- 
troller, C,  is  operated  by  the  home  semaphore's  movement,  and 
is  closed  when  the  latter  is  at  clear;  while  K  is  a  circuit  breaking 

160 


ELECTRO-PNEUMATIC,  ETC.,  SYSTEMS  161 

arrangement  in  series  with  the  distant  magnet,  and  operated  by 
the  returning  to  the  stop  position  of  the  home  arm,  thereby 
preventing  a  clear  distant  arm  when  the  home  is  at  danger,  an 
occurrence  which  would  be  confusing  to  the  engineman.  Each 
section  is  provided  with  a  track  battery,  6,  and  relay,  R,  as  in 
other  systems.  B  is  the  main  battery  which  operates  the  home 
and  distant  control  magnets,  the  former  through  a  local  circuit, 
the  latter  over  line  wires. 

The  train,  by  short-circuiting  the  track  relay,  open-circuits 
the  main  battery,  and,  by  depriving  the  home  magnet  of  current, 
moves  the  home  blade  to  the  stop  position.  The  distant  also 
assumes  the  caution  position  by  the  action  of  the  circuit  breaker; 
the  distant  blade  of  123  thus  maintaining  this  position  by  reason 
of  its  opened  circuit  controller.  Sometimes  the  latter  is  effected 
by  using  the  polarized  track-circuit  principle,  line  wires  not 
being  then  used. 

Liquid  carbon  dioxide  (C02)  has  numerous  advantages  as  a 
source  of  power,  which  result  from  its  enormous  expansion  at 
almost  any  pressure  desired,  through  the  use  of  proper  valves. 
In  exhausting  at  low  pressure,  or  entering  a  chamber  during 
expansion,  it  precipitates  no  moisture;  in  fact  it  may  be  relied 
upon  to  remove  any  moisture  with  which  it  comes  in  contact, 
since  its  point  of  saturation  is  high. 

The  Hall  electro-gas  signal,  which  uses  this  agent  as  a  motive 
power,  is  now  regarded  as  a  very  high  development  of  the  auto- 
matic semaphore,  and  possesses  inherent  features  which  bid 
fair  to  rank  it  as  a  standard  type.  It  employs  standard  posts, 
case,  and  fittings,  with  additional  special  accessories  for  the 
control  and  reception  of  the  gas  and  flasks.  These  flasks  are 
identical  with  those  used  for  soda  fountain  purposes,  and  are 
about  four  and  one-half  feet  long  and  eight  and  one-half  inches 
in  diameter,  weighing  when  charged  about  150  pounds,  con- 
taining 50  pounds  of  liquid  gas.  Two  such  flasks  are  used  at 
each  signal,  and  are  placed  in  a  chute  near  the  base  of  the 
latter. 

The  flasks  are  provided  with  a  safety  valve  blowing  off  at 
2400  pounds  pressure,  and  when  charged  exert  a  pressure  of 
about  800  pounds  per  square  inch.  In  direct  sunlight,  or  when 
near  a  locomotive  boiler,  this  valve  operates,  although  the  flasks 
will  actually  stand  about  one  and  one-half  times  this  pressure. 


162 


AUTOMATIC  BLOCK  SIGNALS 


Before  passing  to  the  operating  cylinders,  this  is  reduced  to 
about  40  pounds  by  a  reducing  valve. 


In  Figs.  158,  159,  and  160,  the  mechanism  of  this  signal  is 
revealed.    The  first  is  a  front  elevation,  the  second  a  side  view, 


ELECTRO-PNEUMATIC,  ETC.,  SYSTEMS 


163 


and  the  third  a  part  section  showing  important  details  of  con- 
struction.   The  signal  is  a  home  and  distant,  although  a  three- 


109- 


FIG.  159 


position  structure  can  be  equally  well  adapted  to  this  motive 
power.    The  gas  expands  and  exerts  its  force  through  the  verti- 


164 


AUTOMATIC  BLOCK  SIGNALS 


cal  cylinders,  200,  the  semaphores  being  moved  by  the  extended 
cylinder  rods,  70,  the  cylinders  being  movable,  and  the  pistons 


109 


IOQ 


FIG.  160 


fixed  to  the  mechanism  frame.     The  home  signal-control  electro- 
magnet appears  on  the  right  side  and  the  distant  on  the  left; 


ELECTRO-PNEUMATIC,  ETC.,  SYSTEMS  165 

these  magnets,  through  their  armatures,  governing  the  admission 
of  gas  to  the  working  cylinders,  and  are  interposed  as  a  function 
between  the  cylinders  and  flasks. 

The  magnets  are  controlled  by  track  circuits  on  either  line 
wire  or  wireless  systems,  and  are  energized  through  a  local  bat- 
tery. In  connection  with  Fig.  162  such  an  arrangement  will  be 
described.  When  a  blade  has  been  cleared,  it  is  held  in  the  clear 
position  by  latches  controlled  by  the  magnets,  their  release 
allowing  gravity  to  throw  the  same  to  the  stop  position.  The 
home  movement  controls  the  distant  as  in  other  types,  the 
means  by  which  this  is  effected  being  shown  later. 

The  reducing  valve,  31,  whose  gauge  has  two  pointers,  show- 
ing the  supply  and  working  pressures,  is  connected  to  the 
expansion  chamber  and  valves,  100,  the  latter  being  controlled  by 
the  magnets,  the  armatures,  12,  raising  the  link,  109,  and  lever,  108. 
The  reducing  valve  is  also  in  connection  with  the  supply  flask 
through  the  pipe,  82.  The  semaphores  are  held  at  clear  by  the 
clutch  levers,  14  and  15,  which  are  actuated  by  their  attached  ar- 
matures, 7,  moving  before  the  poles  of  the  magnets.  When  the 
signal  is  at  clear,  the  rocking  latch,  21,  holds  it  in  this  position  by 
engaging  with  the  clutch  lever.  The  roller  buffer  levers,  17  and 
16,  keep  the  clutch  lever  from  striking  the  magnet  poles  when 
the  signal  returns  to  the  danger  position,  and  maintain  the  arma- 
ture at  a  short  distance  from  the  pole  tips  when  in  this  position, 
so  that  danger  of  freezing  fast  is  eliminated.  The  magnets,  it 
will  be  seen,  are  double  functioned,  their  front  armatures  opera- 
ting the  gas  valve,  and  rear  armature  holding  the  signal  at 
clear. 

When  the  signal  has  cleared,  the  cut-off  levers,  114  and  115, 
act,  and  cut  off  the  gas  from  the  working  cylinder,  allowing 
it  to  exhaust  at  the  same  time,  they  being  controlled  through 
the  pawls,  116,  pivoted  at  48.  These  pawls  engage  with  the  roller, 
20,  at  the  upper  position,  the  gas  thus  being  shut  off  by  their 
mutual  action,  the  stroke  of  the  cylinder  being  varied  by  chang- 
ing the  point  of  release  and  clutch  engagement.  The  clutch 
casting,  9,  is  fastened  to  the  cylinder  rod,  rod  47  guiding  it.  The 
position  of  9  can  be  changed,  thus  changing  the  stroke.  A  switch, 
85,  is  operated  by  the  rod,  44,  when  the  stud,  19,  is  in  engage- 
ment with  it,  and  rocks  about  a  central  shaft  which  carries 
the  contact  blades. 


166 


AUTOMATIC  BLOCK  SIGNALS 


The  clearing  action  is  as  follows:  When  the  magnets,  39,  are 
energized,  their  armatures,  7  and  12,  are  attracted,  the  gas 
valve  being  thereby  opened  through  the  links,  37,  108,  and  109. 
The  supply  valve,  96  (see  Fig.  161),  is  raised,  while  the  exhaust 
port  is  simultaneously  closed.  Gas  enters  the  cylinder  through 
the  center  of  the  piston,  and  raises  the  former,  thus  clearing 
the  signal.  When  the  latch,  21,  has  moved  past  the  projecting 
finger  of  the  clutch  lever,  15,  the  pawl,  116,  is  raised  by  the 
roller,  20,  the  cut-off  lever,  115,  moving  downward.  The  links, 
109  and  108,  are  thereby  forced  down,  thus  closing  the  supply 


SUJlfl 


FIG.  161 

port,  96,  and  opening  the  exhaust  port,  95.  The  latch,  21, 
through  its  engaging  with  15,  thus  opposes  gravity,  which 
tends  to  move  the  mechanism  to  danger.  As  long  as  the 
armature,  7,  is  attracted,  the  signal  will  remain  at  clear. 

If  the  track  section  becomes  occupied,  armature  7  is  released, 
thereby  causing  lever  15  to  move  back.  This  releases  21, 
and  the  semaphore  moves  to  stop.  A  rapid  downward  move- 
ment is  prevented,  as  the  air  must  be  forced  out  through  the 
partly  closed  check  valve,  98,  the  entrained  air  thus  damping 
this  motion. 

The  expansion  chamber,  30,  is  for  the  purpose  of  allowing  the 
gas  to  expand  and  increase  its  temperature.  As  an  expanding 


ELECTRO-PNEUMATIC,  ETC.,  SYSTEMS  167 

gas  always  lowers  in  temperature,  extracting  heat  from  the 
walls  and  adjacent  parts,  should  freezing  occur  its  particles 
are  too  finely  divided  to  produce  any  untoward  results.  Freez- 
ing, however,  by  solidifying  a  gas  having  such  great  expan- 
sibility, is  a  wasteful  process. 

The  piston  area  is  five  square  inches,  and  with  a  40-pound 
working  pressure,  the  upward  force  is  equivalent  to  200  pounds, 
which  gives  sufficient  margin  for  positive  action.  Should 
greater  pressure  be  desirable,  it  can  be  changed  by  adjustment 
of  the  reducing  valve.  About  12,500  movements  can  be  made 
per  flask,  with  this  working  pressure,  or  250  per  pound  of  gas. 

The  magnets  have  two  windings,  which  are  connected  in 
multiple  when  the  valve  is  being  operated,  the  high-resistance 
winding  being  used  to  hold  the  signal  at  clear.  With  the  polar- 
ized track-circuit  scheme,  when  slow  releasing  clutches  are 
used,  the  second  winding  is  first  disconnected  from  the  battery 
and  immediately  closed  upon  itself  by  a  switch,  the  induction 
current  thus  set  up  (which  opposes  any  change  in  flux)  pre- 
venting the  cores  from  being  at  once  demagnetized  and  retain- 
ing the  armature  in  position. 

The  slow-releasing  clutch-magnets  take  a  current  of  .0113 
ampere  at  4  volts,  or  .045  watt;  and  retain  sufficient  flux  to 
hold  the  semaphore  at  clear  for  2.5  seconds  after  they  are 
disconnected  from  the  battery,  which  gives  ample  time  for 
polarity  reversal,  and  full  energization  in  the  opposite  direction. 
The  valve  requires  .1  watt  for  its  operation,  and  from  four  to 
six  cells  are  used  in  the  battery  to  which  the  magnets  are  con- 
nected. 

In  Fig.  162,  A,  B,  and  C,  are  the  slot  batteries  respectively 
of  the  normal  danger  electro-gas  single-blade  signals,  1,  2,  and  3. 
The  cut  sections,  5,  6, 7,  and  8,  have  track  relays  of  corresponding 
number,  which  produce  the  required  interconnection.  The 
battery,  B,  energizes  the  working  magnets  at  2  through  the 
lower  armature  contacts  of  relays  7  and  6,  and  the  upper  arma- 
ture contact  of  5.  Hence,  when  7  is  short-circuited,  2  will 
clear  by  the  back  contact  of  7,  providing  the  sections  of  6  and 
5  are  unoccupied. 

The  actual  circuits  embodied  in  a  normal  clear,  wireless, 
two-arm,  home  and  distant  electro-gas  semaphore,  for  a  single- 
track  signal  system,  are  shown  in  Fig.  163.  R  is  a  polarized 


168 


AUTOMATIC  BLOCK  SIGNALS 


relay,  whose  neutral  armature  front  contacts  are  connected 
to  the  main  battery,  Q,  and  both  polar  and  neutral  armatures 
to  the  home  semaphore;  P  is  a  polarity  reverser  operating 


FIG.  162 


the  preceding  distant  polar  armature;   N,  a  compound  wound 
and  duplex  armature  magnet  clearing  (through  its  valve  operat- 


FIG.  163 


ing  armature)  the  home  blade,  and  0  the  distant.    Each  has 
two  windings :  one  of  280  ohms,  and  the  other  of  350  ohms. 
These  are  connected  in  multiple  when  the  semaphores  are  to 


ELECTRO-PNEUMATIC,  ETC.,  SYSTEMS  169 

be  cleared;  the  high  resistance  winding  alone  being  used  to 
hold  it  at  clear.  When  the  home  blade  is  cleared,  switch  L 
is  closed,  thus  giving  current  to  the  distant  magnet  from  Q. 
K  is  a  switch  arm  which  is  in  contact  with  the  upper  finger 
when  the  home  semaphore  is  at  clear,  and  with  the  lower  when 
at  stop.  Its  function  is  to  short-circuit  the  280-ohm  winding, 
thus  leaving  in  circuit  only  the  high  resistance  coils.  Switch 
S  connects  the  low  resistance  winding  in  shunt  with  the  high 
resistance  winding,  it  being  open  when  the  distant  blade  is 
clear,  thus  decreasing  the  watts  used. 


CHAPTER  XIII. 
ELECTRIC  LOCKING. 

AN  electric  lock  is  a  device,  electrically  controlled,  which 
interposes  a  small  latch  or  bar  at  a  notch  or  recess  in  a  mov- 
able or  sliding  piece,  so  that  the  latter  cannot  be  given  motion 
except  under  conditions  governed  by  the  lock.  This  moving 
piece  obviously  may  be  a  semaphore,  switch,  or  interlocking 
machine  rod;  in  fact  anything  whose  automatic  control  is 
desired. 

Electric  locking  is  sometimes  introduced  in  mechanical 
levers,  so  that  a  signal  operator  cannot  return  to  caution  a 
clear  distant  that  a  train  has  just  passed,  then  return  the  home 
to  stop;  permitting  him  thereafter  to  set  up  a  false  clear  con- 
dition of  a  conflicting  route  by  the  mechanical  unlocking  that 
takes  place.  The  lock  circuit  is  through  the  rails  of  the  section 
intervening  between  the  home  and  distant  signals,  and  in 
series  with  a  battery  and  the  lock  magnets  of  the  conflicting 
levers.  The  train  may  either  complete  the  circuit  directly  or 
through  the  medium  of  a  relay  contact.  Separate  circuits 
may  also  be  employed  to  lock  the  individual  levers. 

Electric  locking,  as  a  subsidiary  function,  is  treated  of  in 
Chapter  5.  It  is  scarcely  possible  to  design  a  semi-automatic 
connection  arrangement  without  the  use  of  such  locking;  it 
forming  the  simplest  scheme  for  controlling  routes  of  any 
desired  combination. 

When  a  plate  or  rod  connected  to  a  lever  has  a  notch  or 
aperture  into  which  a  securety  held  but  freely  moving  locking 
member  drops,  motion  of  the  former  can  or  cannot  be  effected, 
according  to  the  position  of  the  latter.  Thus  in  Fig.  164,  D 
is  a  rigid  stationary  plate  having  an  aperture,  S',  C  a  movable 
plate  connected  to  the  lever  to  be  locked;  and  L  the  armature 
of  an  electromagnet,  R.  If  A  be  an  unlocking  controller, 
when  it  is  moved  in  the  direction  of  the  arrow  its  contacts 
will  be  closed  and  a  current  pass  from  B  through  R,  raising 

170 


ELECTRIC  LOCKING 


171 


L  and  unlocking  C,  and  thereby  rendering  the  lever  free.    Con- 
flicting routes  may  thus  be  protected  electrically. 

A  section  of  one  form  of  switch  lock  is  given  in  Fig.  165. 
Within  a  suitable  housing,  H,  is  placed  an  electromagnet,  A, 
whose  armature,  B,  carries  a  locking  piece,  F;  the  latter  engaging 


with  a  slot  or  recess  in  a  rod,  E,  connected  mechanically  with 
the  switch  point.  Before  the  switch  can  be  thrown,  E  must 
be  free  to  move,  which  will  not  be  the  case  if  the  armature  is 
down,  due  to  the  locking  which  occurs  by  F  falling  into  both 
a  slot  in  the  boss,  Z),  and  the  rod  slot.  When  current  passes 


J/rV^S8SS^0 
'  //  Ss  /7~S///  /  / 


FIG.  165 

around  A,  B  will  be  raised  and  E  free  to  move.  At  G  another 
form  of  recess  is  shown,  which  has  obvious  advantages.  B  is 
carefully  adjusted  by  means  of  the  pivot  screws,  C. 

Electric  locks  are  most  frequently  used  to  regulate  inde- 
pendently the  function  of  the  devices  they  are  supplementary  to. 


172 


AUTOMATIC  BLOCK  SIGNALS 


As  their  application  is  varied,  a  large  number  of  different  types 
are  in  use.  In  Fig.  166  an  electric  lock  applied  to  a  mechan- 
ical interlocking  machine  is  shown.  The  armature,  F,  of  the 
electromagnet,  M,  carries  a  locking  piece,  E,  which  rests  between 
the  stationary  lugs,  A,  and  a  recess  in  the  piece  at  the  rear  of  D, 
which  is  integral  with  the  dog,  G,  of  the  locking  bar,  C;  hence  C 
cannot  be  moved  unless  M  is  energized.  B  is  a  banner  which 
moves  before  an  aperture  in  the  housing,  H,  and  is  secured 
to  the  lock  piece,  E,  serving  as  an  indicator  to  the  operator 
of  the  position  of  the  lock  bar. 

Electric  locking  is  sometimes  applied  as  an  intermediary  to 


FIG.  166 

derails  or  switches,  so  that  the  cleared  home  signal  (mechanical) 
of  an  approaching  train  renders  effective  this  locking,  the 
release  being  arranged  to  act  subsequently,  providing  the 
train  has  entered  an  unlocking  track  section  and  the  home 
signal  has  been  thrown  to  the  stop  position:  the  latter  having 
to  occur  prior  to  the  passing  out  of  the  train  from  the  releasing 
section.  This  leads  to  the  consideration  of  electric  releases 
(although  mechanical  releases  have  been  more  extensively 
applied). 

Electric  releases  are  adjuncts  which  allow  of  a  temporary 
manipulation  of  interlocked  devices  by  the  introduction  of  a 
supplementary  or  compensating  feature;  so  that  the  interlock- 


ELECTRIC  LOCKING 


173 


ing  machine  can  be  set  normal  under  specific  conditions. 
This  release  must  be  returned  to  its  normal  state  (and  con- 
sequently the  electric  locking  made  effective)  before  any  routes 
can  be  set  up  for  approaching  trains. 

In  Fig.  167,  B  is  a  battery  in  series  with  which  is  connected 
a  stick  relay,  R,  and  the  normally  open  contact-springs,  C;  and 
whose  armature  contact  is  in  series  with 
the  normally  open  contacts,  K.  N  is  a 
nut  which  moves  along  the  threaded  rod, 
A,  when  the  crank,  H,  is  revolved.  When 
N  is  moved  upward,  the  contacts,  K,  are 
closed,  but  B  discharges  no  current  as  the 
armature  of  R  is  down.  When  N  strikes 
C,  the  latter  are  closed,  thus  allowing 
a  current  to  pass  through  R.  M  is  a 
circuit  controller  operated  by  throwing 
the  lever  to  which  it  is  attached,  while 
T  is  a  locking  relay  in  series  with  the 
contacts,  K,  and  energized  when  they 
are  closed.  To  require  the  return  of  N 
to  the  normal  position,  both  C  and  K 
must  be  opened,  as  the  battery  will  have 
two  multiple  paths  for  the  current,  the 
first  through  the  front  contact  of  the 
locking  relay,  its  coils,  the  circuit  con- 
troller, and  lock;  the  second  through 
the  contacts,  K,  the/  armature  of  R,  the 
coils  of  R,  and  the  circuit  controller, 
the  lock,  T,  being  thus  shunted,  and 
consequently  deenergized.  When  K-K 
opened,  however,  this  will  not 


arc 


FIG.  167 


occur,  and  the   locked  functions  will   be 
released. 

This  release  arrangement  is  placed  at  some  distance  from  the 
operator,  so  that  some  time  will  be  taken  to  reach  it,  and  this, 
in  addition  to  that  required  in  moving  N  up  and  down  suffices 
to  give  the  requisite  time  before  the  signal  can  be  cleared  for  the 
changed  route,  assuring  greater  safety  thereby. 

Fig.  168  is  a  section  of  the  sector  block  and  lock  employed  in 
the  Coleman  arrangement.  Within  the  housing,  which  is 


174 


AUTOMATIC  BLOCK  SIGNALS 


fastened  to  the  frame  of  the  interlocking  machine,  is  the  sector 
block,  S,  which  is  moved  about  a  center  by  the  link,  (7,  fastened 
to  the  lever,  D,  secured  to  the  square  shaft,  G.  D  is  connected  to 

the  unlocking  segment,  so  that 
whenever  the  operator  raises  the 
latch  preparatory  to  throwing 
the  lever,  it  will  describe  an 
arc.  Within  the  case  is  an 
electromagnet  whose  armature 
extension,  B,  drops  into  a  slot,  P, 
in  the  sector,  a  coinciding  slot 
being  also  in  the  case.  Hence, 
when  the  electromagnet  is  de- 
energixed,  B  will  fall  into  the 
slot  and  securely  lock  S.  B 
also  carries  a  banner  through 
the  projecting  rod,  H,  which 
passes  before  an  aperture,  A,  in 
the  case,  and  indicates  to  the 
operator  the  position  of  B. 

By   providing   a  circuit  con- 
troller connected  to  a  battery 

circuit  in  which  a  locking  electromagnet  is  included,  it  is  evident 
that  a  distant  signal's  movement  may  be  employed  to  govern 
the  movement  of  an  interlocked  lever.  In  Fig.  169  we  have  an 
interlocking  magnet,  B,  applied  to  the  lever,  A,  in  such  a  manner 


FIG.  168 


I   C 


FIG.  169 

that  when  its  armature  is  down,  motion  of  A  in  the  reverse 
direction  cannot  be  effected.  When  the  interlocked  lever  has 
been  thrown  to  its  normal  position,  and  the  distant  signal  arm 
fails  to  assume  the  caution  position,  since  the  contacts  at  the 
controller,  C,  are  open,  it  is  not  possible  to  throw  the  lever  of  the 


ELECTRIC  LOCKING  175 

home  signal,  H,  to  its  full  normal  position.  Hence  such  a  route, 
and  all  other  conflicting  routes,  are  successfully  locked  until  D 
has  been  cleared,  thus  raising  the  armature  of  B  by  the  current 
from  F.  This  provision  is  sometimes  required  to  preclude  the 
possibility  of  D's  not  working  properly  with  its  lever.  Such  an 
arrangement  does  not  interfere  with  keeping  both  home  and  dis- 
tant signals  in  their  proper  relation,  or  their  normal  indications, 
providing  the  levers  are  manipulated  in  proper  sequence. 

Fig.  170  combines  the  simple  interlocking  of  the  lever  of  the 
above  case  with  an  indicator  and  magnetic  controller,  the  signals 
being  in  the  clear  position.  C  is  in  the  latter  position,  due  to  its 
electromagnet  being  deenergized,  a  condition  occurring  when 
B  is  open.  Thus  C  operates  in  unison  with  the  distant  signal, 
and  if  B  is  closed,  will  be  in  the  caution  position.  The  move- 
ment of  the  armature  of  C,  beside  setting  the  miniature  signal, 


FIG.  170 

connects  the  electric  lock,  A,  in  shunt  with  its  magnet,  thus  ener- 
gizing the  former  and  releasing  the  lever.  This  release  is  usually 
effected  on  the  latch  of  the  lever  which  must  be  loose  before  the 
latter  can  be  moved  over  its  quadrant.  Not  only  is  less  energy 
required  to  move  the  locking  member  in  this  case,  but  the  liability 
to  stick  is  also  much  less.  The  purpose  of  the  above  arrangement 
is  to  set  the  signals  hi  their  normal  position,  and  still  require 
that  the  distant  signal  be  at  caution  before  a  route  can  be  altered. 
A  circuit  arrangement  for  the  switch  lock  of  an  outlying 
switch  controlled  from  the  signal  cabin  is  shown  in  Fig.  171. 
The  operator's  hand  switch,  C,  is  a  two-point  arrangement,  the 
left-hand  contact  of  which  is  connected  to  the  relay,  Z),  and  in 
series  with  the  contact,  G,  at  the  switch,  B.  S  is  a  mechanically 
operated  home  signal  having  the  circuit  controller  or  commutator, 
F,  the  latter  being  in  series  with  the  switch-lock  magnet  and 
relay,  H,  so  that  when  S  is  cleared  H  is  deenergized,  and  con- 


176 


AUTOMATIC  BLOCK  SIGNALS 


sequently  locks  B.  H  also  has  an  armature  and  contacts,  7, 
while  M  is  a  push-button,  or  switch,  at  B;  L  is  a  bell,  connected 
to  one  side  of  the  main  battery,  the  latter  being  also  connected 
to  the  common  line-wire. 

If  a  freight  train  at  the  siding,  B,  desires  to  move  to  the  main 
line,  the  conductor  presses  the  button,  M,  which  causes  L  to  ring 
in  the  cabin.  If  the  operator  can  allow  the  switch  to  be  thrown 
open,  he  moves  the  hand  switch  lever  to  the  right-hand  contact. 
If  F  be  closed,  a  current  will  pass  from  the  main  battery  over 
the  common  line-wire  to  H,  F,  E,  and  (7,  thus  energizing  H 
and  releasing  the  lock.  A  train  cannot  now  pass  in  the  direc- 
tion of  the  arrow,  since  the  semaphore  at  S  is  at  danger. 


M- 


1 I 


line 


FIG.  171 


Also,  if  the  lock,  7),  were  energized,  its  armature,  E,  would  be 
raised,  thus  opening  the  circuit  and  preventing  H  from  being 
energized.  The  train  could  not  proceed  from  B  if  S  were  at 
clear,  as  F  would  be  opened. 

Should  a  train  desire  to  proceed  from  the  siding,  A,  to  the 
main  line,  the  reverse  operations  occur,  the  hand  switch  lever 
being  moved  to  the  left-hand  contact.  A  current  then  passes 
through  D,  raising  its  armature  and  releasing  the  switch  lock. 
C  must  now  be  closed  and  H  deenergized,  so  that  the  armature, 
7,  will  close  the  circuit.  This  cannot  occur  if  the  switch  at  B  is 
open,  or  H  is  energized.  7),  however,  may  control  a  signal,  so 
that  a  train  movement  on  the  main  track  can  be  allowed  only 
when  it  is  energized  ;  that  is,  C  must  be  in  the  left-hand 
position. 


ELECTRIC  LOCKING 


177 


In  Fig.  172  a  control  circuit,  such  as  is  used  in  connection  with 
a  train  staff  on  a  single-track  line  with  sidings,  is  shown.  The 
main  line  is  connected  to  a  siding  by  the  switch,  1.  From  the 
block  tower,  9,  the  home  signals,  2  and  22,  are  operated,  11  being 
a  circuit  breaker  operated  by  the  semaphore  of  2,  while  17  is 
operated  by  the  insertion  of  a  train  staff;  and  when  the  latter  is 
closed,  relay  19  is  energized. 

The  removal  of  the  staff  opens  this  circuit,  but  the  relay 
remains  energized,  since  a  current  flows  through  it  by  reason 
of  the  armature,  18,  of  the  4-ohm  track-relay,  23,  being  up. 
This  also  closes  the  slot  circuit,  causing  a  current  to  pass  through 


FIG.  172 

the  coils  of  a  slot  or  lock  magnet,  3,  whose  armature,  4,  .controls 
the  movement  of  the  main  line  signal,  2,  which  must  be  cleared 
in  order  to  allow  a  train  to  proceed  in  the  direction  of  the 
arrow.  When  22  has  been  cleared,  which  will  occur  when  the 
switch,  1,  has  been  opened,  a  staff  is  inserted  and  therefore  the 
circuit  closer,  7,  operated. 

When  this  signal  is  cleared,  the  circuit  through  the  lock 
magnet,  13,  is  broken  at  11,  which  allows  the  locking  function, 
14,  to  fall,  the  latter  locking  the  switch  rod  in  place.  The 
switch  cannot  therefore  be  opened  until  a  train  has  passed 
over  the  insulated  section  to  which  the  4-ohm  relay  is  connected. 
The  engineman  of  a  train  passing  into  the  protected  section 


178  AUTOMATIC  BLOCK  SIGNALS 

removes  the  staff  at  7,  thus  opening  this  circuit  and  causing  2 
to  pass  to  the  danger  position.  The  track  being  short-circuited, 
the  5-ohm  relay,  19,  is  deenergized,  and  the  9-ohm  relay,  10, 
energized.  After  the  entire  train  has  passed  over  the  track 
section  across  which  a  difference  of  potential  is  maintained 
by  the  battery,  8,  the  4-ohm  relay  is  again  active,  which  allows 
the  switch  to  be  thrown  to  its  normal  position. 

The  signal,  6,  may  be  a  distant  signal,  or  one  showing  the 
condition  of  the  main  line  for  trains  taking  the  siding.  15  and 
5  are  slot  batteries,  and  the  armature,  18,  has  a  lower  contact, 
21,  which  is  in  series  with  12  and  10.  16  is  a  hand  switch  pro- 
vided to  unlock  13  through  battery  15,  in  case  it  becomes 
necessary  to  move  a  train  in  one  direction  before  another  can 
proceed  to  that  point. 

Detector  bars  may  sometimes  be  replaced  by  short  insulated 
track  sections  introduced  at  the  switch  to  be  governed,  electric 
locking  being  also  provided.  In  electrical  power  interlocking, 
special  track  relays  having  contacts  capable  of  carrying  and 
breaking  heavy  currents  are  necessary.  These  have  non- 
fusing  carbon  contacts  of  great  area,  a  wide  break  being  inter- 
posed when  the  relay  operates,  in  some  cases  requiring  also  a 
magnetic  blow-out.  The  locking-circuits  are  usually  independ- 
ent of  the  power  circuits  control  in  such  cases;  but  their  appli- 
cation need  not  be  entered  into  here. 


CHAPTER  XIV. 
ALL-ELECTRIC  INTERLOCKING. 

NUMEROUS  types  of  interlocking  are  in  use,  in  which  the 
operative  agencies  are  either  partly  mechanical,  or  mechanical 
with  electrical  control.  The  General  Railway  Signal  Co.,  how- 
ever, manufacture  apparatus  in  which  both  working  and  control 
functions  are  electrical,  a  mechanical  interlocking  frame  being 
used  as  an  auxiliary  to  the  levers.  An  early  form  of  this 
apparatus  (known  as  the  Taylor)  will  first  be  described. 

In  Fig.  173  the  connections  at  a  double  route  signal,  37, 
having  two  home  blades,  one  of  which  protects  the  main  track 
and  the  other  a  diverging  track,  44,  are  shown.  A  derail,  28,  is 
also  in  the  block  of  37,  and  is  operated  by  a  motor,  12.  This 
diagram  is  completed  by  Fig.  174,  which  represents  the  con- 
nections at  the  interlocking  cabin  pertaining  particularly  to  37. 
The  motor,  49,  operates  44;  28  is  thrown  by  12,  while  both  arms 
of  37  are  cleared  by  31.  The  line  wires,  1,  2,  3, 4,  5,  6,  7,  8,  and 
9,  pass  to  the  interlocking  machine,  45  and  38  running  to  the 
distant  signal  protecting  the  home  block  of  37. 

The  motor,  31-32,  operates  either  of  the  home  semaphores, 
according  to  which  selector  magnet,  29  or  30,  is  energized.  A 
circuit  controller,  33,  is  hi  circuit  with  the  motor,  31,  and  the 
brake  magnet,  26.  The  contacts,  46,  are  in  series  with  the  wire 
feeding,  31  and  26,  and  are  provided  so  that  a  clear  signal  will 
not  be  given  when  the  derail  is  open.  Should  the  derail  be  in 
the  opposite  or  safe  position,  these  contacts  will  be  closed. 
Such  a  precaution  is  necessary  in  high-speed  train  movements, 
as  an  open  derail  would  cause  a  wreck. 

The  track  is  energized  by  the  battery,  27,  the  relay  being 
omitted.  The  rotation  of  12,  and  consequently  the  throwing 
of  28,  moves  the  pole  changer,  18,  the  function  of  which  will 
be  shown  later.  At  44,  the  motor,  48-49,  is  also  connected  to 
a  pole  changer  operated  by  the  switch  movement.  Contacts 
11  are  controlled  by  44,  being  closed  when  the  latter  is  open, 

179 


180 


AUTOMATIC  BLOCK  SIGNALS 


while  the  contacts,  10,  are  at  the  same  time  open.  10  is  in  series 
with  30,  and  11  in  series  with  29,  so  that  when  one  semaphore 
at  signal  37  is  cleared,  the  other  cannot  be,  since  but  one  route 
at  a  time  can  be  set  up. 


I.Z.3.f:5.6?89. 


FIG.  173 


In  Fig.  174  the  connections  at  the  cabin  are  shown.  B  is  a 
60-volt  storage  battery;  115,  116,  117,  and  118  are  track  relays, 
having  contact  armatures,  133  to  136,  for  carrying  heavy  cur- 
rents; 119  to  122  are  latch-releasing  magnets,  which  when  ener- 


ALL-ELECTRIC  INTERLOCKING 


181 


182  AUTOMATIC  BLOCK  SIGNALS 

gized  permit  the  levers  (bars  with  handles,  having  a  horizontal 
movement)  to  which  they  are  connected  to  be  moved;  123  to  132 
are  indication  magnets,  which  give  an  indication  of  switch  or  sig- 
nal movements;  while  the  row  of  switches  in  the  lower  part  of  the 
figure  are  pole  changers  and  connectors  actuated  by  the  levers 
themselves  when  the  latter  are  thrown.  The  wires,  79,  pass  to 
the  ends  of  the  sections  in  which  the  track  relays  are  introduced ; 
the  lines,  1  to  14  (only  1  to  9  are  relevant  to  this  description), 
run  to  the  arrangement  given  in  the  preceding  figure,  and  have 
the  same  significance;  80  and  83  pass  to  preceding  switches, 
while  81  and  82  are  signal  wires.  84  is  a  common  wire  connect- 
ing one  side  of  the  battery,  all  the  electromagnets,  and  several 
of  the  line  wires.  There  are  10  lever  (the  levers  themselves 
being  omitted)  circuits;  they  being  distinguished  by  the  fact 
that  each  has  an  indication  magnet;  signal  levers  opening  one 
contact  and  closing  another,  while  the  switch  levers  open  two 
circuits  and  close  two  during  movement. 

The  armatures,  153  and  136,  also  133  and  134,  are  in  series, 
so  that  should  either  fall  the  circuit  will  be  opened.  Lines  7 
and  10  are  connected  to  84;  while  11  is  a  battery  line  in  series 
with  135  and  136;  12  and  13  being  switch  lines  and  14  a  signal 
line.  In  tracing  up  a  lever's  circuit,  it  should  be  remembered 
that  the  order  is  changed  after  a  rail  switch  or  signal  has  been 
thrown,  by  reason  of  the  electric  switches  thus  opened  or  closed, 
and  that  single  switches  are  for  signal,  and  double  switches  for 
switch  movement. 

Consider,  for  instance,  signal  lever  123.  (The  levers  are  sup- 
posed to  have  the  same  numbers  as  the  indication  magnets.) 
When  the  lever  is  "  thrown  "  137  will  be  disconnected  from  138, 
and  123  therefore  deenergized.  Immediately  after,  138  will  be 
connected  to  139,  and  a  current  flow  from  B  to  line  80,  and  the 
signal  (provided  conditions  are  safe)  at  the  latter. 

Considering  switch  lever  131 :  When  the  switch  is  closed  by 
the  lever  a  current  flows  from  B  through  134  and  133-72  and 
71-line  wire  9-  to  Fig.  173-25  and  23-49-22-21-24-48-line  7- 
Fig.  174-  common  wire  84,  and  back  to  B.  Since  48-49  begins 
its  rotation,  the  switch  is  thrown  and  the  current  reverser  20-25 
is  operated,  so  that  the  next  time  131  is  thrown  the  motor  arma- 
ture will  revolve  in  the  opposite  direction,  and  consequently 
moves  the  switch  back  to  its  former  position.  The  current  will 


ALL-ELECTRIC  INTERLOCKING  183 

then  pass  through  line  8  instead  of  7.  The  switch  movement 
cannot  occur  unless  115  and  116  are  both  energized,  which 
requires  of  course  a  clear  track  and  the  absence  of  conflicting 
routes.  Relay  116  is  connected  to  track  battery  27  through 
the  rails  of  the  track  between  37  and  the  next  signal,  while  115 
is  connected  to  the  side  route  extending  beyond  switch  44. 
Hence  when  either  115  or  116  is  deenergized,  44  cannot  be 
thrown. 

The  reverse  and  normal  currents  to  switch  44  are  through  the 
contacts,  133  and  134,  as  train  movement  over  this  switch  may 
take  place  in  either  position,  since  it  joins  two  routes.  The 
reverse  current  is  not  required  through  the  relay  contacts  in 
case  of  a  derail,  as  a  train  does  not  move  over  such  a  switch 
when  normal;  and  sometimes  it  is  necessary  to  reverse  it  when 
the  block  is  occupied,  that  is,  when  the  track  relay  is  deenergized. 

Lever  127  is  for  switch  28,  and  levers  132  and  128  are  for  30 
and  29  respectively  of  the  semaphores  at  signal  37.  Tracing  up 
the  connections  for  127,  we  have,  considering  that  this  lever  has 
been  pulled  outward  (and  consequently  contacts  52  and  53, 
55  and  56  separated;  with  53  connected  to  54,  and  56  to  57), 
5-101-54-53-line  4-Fig.  173-17-  19-12-18-16-15-13-line  6- 
Fig.  174-140-124-84-5.  By  reason  of  the  movement  of  the 
switch,  by  the  rotation  of  12,  the  polarity  changer,  18-19,  is 
reversed,  so  that  18  and  19  are  disconnected  from  16  and  17  and 
connected  to  14  and  15.  This  closes  the  indication  circuit  and 
causes  a  current  to  flow  from  the  switch  motor,  12,  through  18- 
14-line  3-56-57-120-84-line  6 -Fig.  173-13-15-18.  Thus  120 
is  energized,  the  lever  latch  is  released  and  the  latter  can  com- 
plete its  stroke.  This  releases  the  lever  of  30  (132)  so  that  the 
lower  semaphore  of  37  can  be  cleared.  When  132  is  reversed, 
77  is  disconnected  from  76  and  connected  to  78.  A  circuit  is 
thus  closed  including  5-101-78-77-line  1-Fig.  173-line  1-con- 
tacts  11,  (which  are  under  the  control  of  44 )-29-3 1-32-34-33- 
3^46-13-line  6-Fig.  174-140-124-84-5. 

The  clearing  of  the  semaphore  connected  to  29  moves  33  in 
a  downward  direction  and  thus  shunts  the  above  circuit  with 
the  brake  magnet,  26.  As  long  as  132  is  reversed,  the  upper 
semaphore  of  37  will  be  at  clear,  while  the  connecting  of  35  with 
36  clears  the  distant  signal  preceding  37.  Should  132  be 
returned  to  its  normal  position,  77  will  be  in  contact  with  76,  as 


184  AUTOMATIC  BLOCK  SIGNALS 

in  the  figure.  When  the  signal  is  returning  to  danger,  33  again 
connects  34  and  36,  thus  closing  the  circuit  through  the  motor 
31-32,  and  the  indication  magnet,  132,  of  Fig.  174. 

The  effect  of  gravity  is  to  give  the  armature,  31,  a  rapid  rate  of 
revolution,  which  sets  up  a  counter  current  and  dampens  the 
fall  of  the  blade.  This  current  passes  momentarily  through 
the  brake  magnet,  26,  which  in  addition  to  the  retardation  of 
the  motor  armature,  prevents  injury  to  the  moving  system 
from  inertia.  The  energization  of  132  also  releases  the  lever 
latch  and  allows  the  lever  to  complete  its  movement,  which 
could  not  occur  did  this  release  current  not  flow. 

It  will  be  noted  that  the  indication  furnishes  to  the  operator 
the  right  to  complete  the  lever  stroke,  since  it  occurs  after 
the  lever  has  started.  This  is  similar  in  function  to  that  of 
other  schemes  of  power  interlocking,  the  indication  showing 
that  the  switch  has  completed  its  movement.  This  indication 
is  used  only  on  the  switch  levers,  as  will  be  noted  in  Fig.  174, 
there  being  but  four  such  indication  magnets. 

A  later  development  of  the  above  circuit  arrangements  is 
shown  in  Fig.  175,  in  which  the  track  circuits  (which  may  be 
either  polarized  or  neutral)  are  not  considered.  In  defining 
the  functions  and  their  relativity,  the  previous  figures  will 
not  be  considered,  although  an  extension  of  the  principle  to 
a  more  elaborate  though  concentrated  and  isolated  case  is  the 
object  in  view.  Two  sets  of  interconnected  (by  eight  lines  or 
wires  in  underground  conduits)  circuits  are  shown:  first,  those 
at  the  interlocking  cabin;  and  second,  those  at  a  distant  signal, 
1,  a  high  home  signal,  2  (protecting  two  separate  routes),  a 
switch  movement,  3,  and  a  dwarf  signal,  4  (the  single  sema- 
phore home  signal,  5,  being  for  movements  in  the  opposite  direc- 
tion, and  its  circuits  therefore  not  shown). 

The  tappet  bars  are  given  a  vertical  movement  by  the  levers; 
cross  locking  being  effected  by  the  dogs,  d,  which  are  affixed 
to  sliding  horizontal  bars,  and  the  recesses,  b,  cut  in  the  tappet 
bars.  If  a  dog  engages  with  a  recess,  and  the  former  is  immov- 
able, it  is  evident  that  the  lever  to  which  this  locked  tappet 
bar  belongs  cannot  be  moved.  In  the  figure,  levers  1,  2,  and 
4  are  immovable;  that  is,  they  are  mechanically  locked  in 
position.  Lever  3  is  movable,  however,  since  it  is  not  engaged 
by  any  dog,  and  if  it  be  pulled  outward,  its  tappet  bar  will 


ALL-ELECTRIC  INTERLOCKING 


185 


nn*  ,     rh  , 


^=B^ 


186  AUTOMATIC  BLOCK  SIGNALS 

rise,  thus  unlocking  levers  1,  2,  and  4,  since  their  dogs  are  now 
released  by  the  action  of  the  recesses.  The  levers  operate 
the  signals  and  switch  of  the  same  numbers,  hence  the  latter 
are  locked  in  the  same  fashion.  It  is  thus  evident  that  switch 
3  must  be  thrown  before  the  signals  can  be  cleared,  this  sequence 
being  manifestly  required. 

The  cam  slot  in  the  lever  transmits  an  intermittent  motion 
.to  the  corresponding  tappet  bar,  which  is  for  the  purpose  of 
preparing  for  a  change  in  the  circuits  to  which  the  lever  is 
mechanically  connected.  The  circuit  controller  consists  of 
stationary  and  movable  contact  pieces,  whose  relation,  though 
not  their  actual  construction,  is  as  shown. 

The  dwarf  signal  lever  (4)  and  the  switch  lever  (3)  have 
each  eight  stationary  contacts;  the  two  remaining  levers  having 
but  four,  the  reasons  for  which  will  appear  later.  The  first 
half  of  the  outward  movement  of  levers  1,  2,  and  3  produces 
no  change  in  the  connections,  since  the  movable  contacts  engage 
the  same  brushes,  and  constitute  the  preliminary  locking  move- 
ment for  the  conflicting  routes  affecting  this  lever. 

The  central  part  of  the  lever  stroke  moves  the  contact  pieces 
to  the  sets  of  brushes  on  the  opposite  side  the  tappet  bar 
being  stationary.  The  further  motion  of  the  lever  is  opposed 
by  the  latch,  L  (or  L1,  L2,  etc.),  which  can  only  be  released  by 
the  energization  of  the  indication  magnet,  7,  which  will  allow 
of  its  travel  being  continued  until  the  end  of  the  stroke  is 
reached.  This  final  movement  further  raises  the  tappet  bar, 
releasing  the  dogs  and  bars  controlling  conflicting  routes,  and 
preserving  the  connections  obtaining  at  the  beginning  of  the 
last  half  of  the  stroke.  The  switch  movement  will  first  be 
considered. 

To  the  main  common  line  the  indicator  common,  all  the 
signals,  and  the  switch  movement  are  connected,  either  directly 
or  through  a  circuit-breaker  contact.  The  switch  movement 
is  controlled  by  two  other  wires,  through  which  the  indication 
current  passes,  with  the  indicator  common.  The  control  wire 
in  the  normal  position  is,  in  the  reverse  position,  the  indicator 
wire,  both  being  used  at  a  time.  These  two  wires  are  connected 
to  opposite  brushes  of  the  circuit  controller,  so  that  reversal 
of  polarity  can  be  effected  by  straight  motion  of  the  controller 
rod  from  the  lever.  In  the  position  shown  (which  is  normal) 


ALL-ELECTRIC  INTERLOCKING  187 

the  indicator  wire  is  connected  to  the  indication  common 
through  the  indication  magnet,  I3,  and  the  indication  bus-bar, 
while  the  control  wire  is  connected  to  the  positive  side  of  the 
battery  through  the  safety  magnet,  S,  and  the  operating  bus- 
bar. In  the  reverse  position  these  connections  are  reversed, 
as  above  stated. 

Additional  control  of  the  switch  movement  is  effected  by 
the  polarity  changing  arrangement,  P,  which  is  operated  by 
the  switch-lock  bolt  after  it  has  passed  through  the  lock  rod  and 
adjacent  plates.  This  pole  changer  has  eight  fixed  contacts 
and  two  movable  contact  plates.  Each  of  the  motor  armature 
terminals  is  connected  to  two  of  these  fixed  contacts,  each  con- 
trol wire  to  one,  and  one  of  the  field  terminals  to  the  remaining 
two,  the  other  field  terminal  being  joined  to  the  main  common. 
This  connection  arrangement,  through  the  action  of  the  other 
movable  contacts,  connects  in  the  one  case  (that  shown,  or 
normal)  A  to  the  indicator  wire  and  b  to  the  field,  F3;  and  in 
the  reverse  position,  A  to  the  field  and  6  to  the  reverse  indicator 
wire.  In  the  former  position,  also,  the  pole-changing  switch  is 
disconnected  from  the  normal  control;  no  current  flowing, 
although  this  control  is  connected  to  the  battery.  Reversal 
of  the  switch  lever,  however,  will  connect  the  reverse  control 
wire  with  the  battery,  a  current  flowing  through  the  following 
circuit: 

Battery- K-operating  bus-safety  magnet,  /S-circuit  controller 
contacts,  6  and  8-reverse  control  wire-contacts  16  and  15-A3- 
contacts  11  and  12-jP3-main  common-battery.  When  the 
switch  has  completed  its  movement  and  is  locked  in  position, 
the  lock  rod  throws  the  pole  changer,  so  that  contact  9  is  con- 
nected to  10,  and  13  to  14.  The  reverse  control  wire  is  thus  dis- 
connected from  the  armature,  6,  and  connected  to  the  reverse 
indication  wire,  while  a  is  connected  to  the  field  coils;  the  rea- 
sons for  which  will  appear  shortly. 

The  safety  magnet,  S,  and  the  indication  magnet,  73,  both  have 
their  poles  facing,  and  capable  of  acting  upon  the  armature,  T\ 
this  armature  normally  resting  upon  the  poles  of  the  safety  mag- 
net, which  is  in  series  with  the  battery  and  both  control  wires; 
the  one  in  circuit  depending  upon  the  positions  of  P  and  the 
switch  lever  circuit  controller.  Should  a  break  occur  in  any  of 
these  wires  or  in  the  safety  magnet,  coils  S  will  not  be  energized. 


188  AUTOMATIC  BLOCK  SIGNALS 

If  a  cross  or  short  circuit  occurs  between  the  control  wires,  the 
total  current,  both  that  passing  to  the  switch  motor,  and  that 
through  the  indication  magnet,  will  pass  around  S,  so  that 
should  all  the  current  pass  through  the  indication  magnet  on 
return,  it  will  not  exceed  the  current  in  the  former;  hence  the 
armature  will  be  held  by  S,  and  the  indication  cannot  be  given. 
As  the  armature  normally  rests  upon  the  poles  of  S,  in  which 
case  the  air-gap  is  zero,  and  the  magnetic  reluctance  low, 
this  probability  is  further  increased.  Thus  it  is  practically 
impossible  for  a  cross  to  set  up  a  false  indication. 

A  motor  when  operating  sets  up  a  counter  electro-motive 
force  which  opposes  that  of  the  operating  current.  If  the  latter 
be  suddenly  cut  off  and  the  armature  immediately  connected  to 
an  independent  circuit,  a  current  will  flow  in  the  latter  (its 
strength  determined  by  the  counter  e.m.f.  and  total  resistance 
in  the  circuit)  in  the  opposite  sense  to  that  of  the  driving  cur- 
rent; and  will  be  maintained  by  the  inertia  of  the  armature  and 
mechanically  connected  parts.  This  is  precisely  the  effect  which 
is  utilized  to  give  an  indication  through  73,  the  proper  connec- 
tions being  effected  by  the  pole  changer.  The  circuit  thus 
formed  for  the  indication  current  is:  terminal  a-F3-mam  com- 
mon-indicator common-magnetic  cut-out,  ^-switch  J-indi- 
Cation  bus-/3-circuit  controller  contacts  4  and  2-reverse 
indication  line—pole  changer  contacts  10  and  9-armature  ter- 
minal 6.  The  current  thus  flows  in  the  same  direction  as  before 
through  the  field,  hence  its  magnetic  flux  is  unaltered,  while 
the  indication  magnet  releases  the  switch  lever  by  reason  of  the 
following : 

Normally,  the  latch,  L3,  is  held  in  the  position  shown  by  the 
dog,  P3,  and  prevents  full  outward  movement  of  the  lever  by 
the  engaging  of  projection  Q3  with  the  projection  on  the  right- 
hand  end  of  L3.  When  P  is  energized,  however,  T3  is  moved 
upward,  and  its  rod  strikes  dog  P3  so  that  L3  is  released  and 
allowed  to  drop,  permitting  the  completion  of  the  lever  stroke. 
(It  should  be  remembered  that  the  travel  of  the  lever  has  already 
been  traced  to  its  middle  position.)  Hence  the  indication  cur- 
rent cannot  be  set  up  before  the  motor-operating  current  has 
been  cut  off,  the  indication  wire  connected  to  one  side  of  the  ar- 
mature, and  the  connections  between  armature  and  field  re- 
versed. The  cessation  of  operating  current  might  be  produced 


ALL-ELECTRIC  INTERLOCKING  189 

by  a  broken  conductor,  which  is  a  highly  improbable  condition, 
while  crosses  are  guarded  against  by  S. 

The  magnets,  M  and  M' ,  are  in  series  and  connected  to  the 
indicator  and  control  line- wires,  their  junction  being  also  in 
connection  with  one  terminal  of  F*  and  consequently  the  main 
common.  By  means  of  these  magnets,  the  movement  of  P  is 
under  the  control  of  lever  3,  at  such  times  as  it  is  not  operated 
automatically  by  the  lock  rod.  When  the  battery  is  connected 
to  the  normal  control  wire,  current  energizes  M\  but  when  the 
reverse  control  wire  is  in  connection  with  the  battery,  M'  is 
energized.  These  currents  shift  the  pole-changer  mechanism  hi 
the  direction  of  the  magnet  through  which  the  current  circulates, 
hence  movement  can  be  effected  at  any  time  during  the  switch- 
and  lock-rod-movement,  except  at  the  very  beginning  and  end- 
ing of  the  latter.  If  the  lever  is  used  to  reverse  the  switch, 
current  passes  through  the  motor  and  through  Mf\  this  current 
so  holds  the  pole  changer  that  the  operating  current  will  be 
maintained.  Should  it  be  desirable  to  throw  the  switch  normal 
before  this  reverse  movement  has  been  completed  (which  con- 
tingency might  arise  from  snow,  ice,  or  other  obstruction  between 
the  main  and  point  rails),  the  lever  is  merely  pulled  back  to  the 
normal  position,  thus  energizing  M  through  the  normal  control 
wire  and  throwing  the  switch  back.  This  is  effected  by  M 
shifting  P  to  its  former  position,  sending  current  through  the 
motor  in  the  proper  sense  by  way  of  the  normal  control  wire; 
the  pole  changer  being  again  shifted  to  the  position  shown,  thus 
setting  up  the  indication  current.  When  M  shifts  P,  current 
does  not  pass  through  I3,  since  the  lever  controller  is  not  in  the 
proper  relation  with  the  pole  changer,  and  current  is  not  set  up 
if  the  magnet  refuses  to  operate,  on  account  of  the  reversed 
armature  connections.  A  circuit-breaking  device  is  in  series 
with  M  and  M',  so  that  when  the  switch  has  fully  moved  and  is 
locked  in  either  position,  the  current  is  cut  off  from  these  mag- 
nets. This  does  not  alter  the  rest  of  the  diagram,  however. 

When  the  lever,  3,  is  moved  to  the  normal  position,  the  battery 
is  connected  to  the  normal  control  wire  through  S,  thus  sending 
a  current  through  the  switch  motor,  which  starts  at  a  and 
returns  to  b,  in  the  opposite  sense  to  that  used  in  reversing 
the  switch,  the  field  current  maintaining  its  proper  course. 
The  armature  thus  revolves  in  the  opposite  direction,  the  switch 


190  AUTOMATIC  BLOCK  SIGNALS 

rails  being  thereby  thrown  normal,  and  at  the  completion  of 
this  movement,  P  is  shifted  to  the  position  shown  in  the  dia- 
gram, the  indication  current  being  thereby  set  up.  Terminal  b 
is  thus  open-circuited,  while  a  is  put  in  series  with  the  normal 
indication  wire,  which  at  first  was  the  reverse  control  line. 

The  switchbox  contains  a  pole-changing  device  which  con- 
trols the  motor  of  the  two-home-arm  high  signal,  2.  When  the 
motor  revolves  in  one  direction,  one  of  the  semaphores  is  cleared, 
and  when  in  the  other  direction,  the  remaining  blade.  This 
switch  thus  acts  selectively,  the  semaphore  being  connected 
by  a  chain  to  opposite  sides  of  a  sheave  wheel  driven  by  the 
motor  through  reduction  gearing.  Hence,  when  one  sema- 
phore is  cleared,  the  other  must  be  at  danger,  gravity  producing 
this  latter  condition  through  the  medium  of  counterweighted 
levers,  which  are  mechanically  connected  to  the  blades. 

Each  semaphore  operates  a  circuit  breaker,  the  upper  arm 
having  two  sets  of  contacts,  and  the  lower  one  set.  One  of 
the  former  closes  the  circuit  of  the  distant  signal,  1,  the  lower 
arm  not  having  a  distant  function.  The  lever,  2,  which  con- 
trols this  home  signal,  operates  a  controller  having  one  reverse 
and  one  normal  pair  of  fixed  contacts,  but  one  movable  piece 
being  used.  Only  one  line  wire,  the  control  and  indication, 
passes  to  2,  and  is  in  series  with  72  and  the  lower  set  of  fixed 
contacts.  One  of  the  upper  contacts  is  connected  to  the  indi- 
cating bus,  and  the  other  to  the  operating  bus.  When  lever 
2  is  reversed,  the  positive  side  of  the  battery  will  be  connected 
to  P  and  the  control  line,  a  current  flowing  through  the  cir- 
cuit including  72-control  \me-G2-G-F2-switchbox-a2-A2-b2- 
switchbox-main  common-battery.  If  the  switchbox  is  in  its 
normal  condition,  the  upper  arm  at  2  will  be  cleared.  Upon 
the  completion  of  the  movement  to  clear,  G2  opens  the  home 
circuit  and  closes  the  distant  circuit,  the  motor-brake  magnet, 
B2j  being  in  shunt  across  this  break,  this  magnet  having  a 
comparatively  high  resistance  and  bringing  the  motor  arma- 
ture to  a  stop,  holding  the  signal  at  clear  as  long  as  lever  2  is 
in  this  reverse  position. 

As  P  is  energized,  L2  releases  the  lever,  so  that  the  full 
movement  to  the  reverse  position  can  be  made.  This  energi- 
zation does  not  constitute  an  indication,  as  such  is  not  required, 
since  locking  is  not  released.  The  movement  of  the  distant 


ALL-ELECTRIC  INTERLOCKING  191 

signal,  1,  to  the  clear  position  is  the  only  indication  required  of 
the  proper  clearing  of  this  upper  blade,  this  being  accomplished 
by  the  interposed  circuit-breaker.  When  lever  2  is  pushed 
back  to^  normal,  the  brake-magnet  circuit  is  broken,  and  the 
indication  magnet  connected  to  indication  common  and  the 
control  line.  Hence  the  brake  mechanism  is  released,  the  blade 
returning  to  normal  by  the  action  of  gravity  on  the  counter- 
weight. This  sets  the  train  of  gears  and  motor  armature  into 
rotation,  developing  a  counter  e.m.f.,  the  circuit-breaker,  G2,  also 
closing  the  indication  circuit  in  its  upper  position.  This  circuit 
includes  A2-b2  switchbox-main  common -indication  common- 
#-J-indication  bus-!2-control  line-(r2-(;r-.F2-switchbox-  and  a2. 
The  latch,  L3,  is  thus  released,  so  that  the  final  part  of  the 
stroke  of  the  lever,  3,  can  be  made.  The  energy  expended 
in  this  releasing  circuit  retards  the  moving  armature  and  pre- 
vents a  blow  being  delivered  by  the  moving  parts. 

If  the  switchbox  switch  is  reversed  when  lever  2  has  been  re- 
versed, the  current  will  pass  through  the  armature  from  62  to  a2, 
in  the  opposite  direction  to  that  above  shown.  This,  therefore, 
causes  the  armature  to  revolve  in  the  opposite  direction,  thus 
clearing  the  lower  arm,  the  indication  current  being  developed 
in  the  same  manner  as  above  described,  the  brake  magnet,  B2, 
being  put  in  circuit  by  the  action  of  (7,  with  which  it  will  be 
in  shunt.  The  indication  current  is  also  in  the  opposite  direc- 
tion in  the  armature  and  switchbox. 

The  dwarf  signal,  4,  is  not  thrown  to  clear  through  the  aid' 
of  a  motor,  but  directly  by  the  movable  magnetic  circuit  of  a 
heavy  solenoid.  This  solenoid  has  two  distinct  windings, 
represented  in  the  diagram  by  R  and  W.  R  is  the  retaining 
coil,  and  is  of  high  resistance,  holding  the  small  semaphore  at 
clear,  while  W  is  the  working  or  clearing  coil,  and  of  compara- 
tively low  resistance.  The  indication  current  is  taken  directly 
from  the  working  battery  by  way  of  the  signal's  lever,  4, 
instead  of  utilizing  the  counter  e.m.f.  of  a  motor,  it  serving 
equally  well.  The  circuit  controller  has  eight  stationary  and 
two  movable  contacts  as  before;  four  of  these  fixed  contacts 
being  shorter,  however,  so  that  the  movable  pieces  will  not 
dwell  upon  the  former  more  than  a  predetermined  time. 

A  normally  fixed  connection  exists  between  the  indication 
magnet  and  the  positive  side  of  the  battery,  the  indication  line 


192  AUTOMATIC  BLOCK  SIGNALS 

being  connected  to  but  one  of  the  short  fixed  contacts.  The 
indication  line  is  connected  to  a  circuit-breaker,  Z),  at  the  dwarf 
signal,  another  circuit-breaker,  G4,  being  in  series  with  the  working 
coil.  The  latter  is  closed  only  when  the  signal  lever  is  reversed, 
while  D  is  closed  only  when  the  signal  is  normal.  When  the  lever 
is  at  the  normal  indication  position,  the  control  line  is  connected 
to  the  indication  bus,  and  the  other  end  of  the  indication  magnet 
to  the  indication  wire.  At  the  reverse  indication  position 
(when  the  movable  contacts  are  in  the  dotted  line  denoting  the 
reverse  indication  and  control  points)  the  positive  side  of  the 
battery  is  in  connection  with  the  control  wire,  the  indication 
magnet  being  in  series  with  the  indicator  and  main  common 
lines,  and  the  negative  side  of  the  battery. 

At  the  full  normal  and  reverse  point,  the  indication  magnet  is 
open-circuited,  and  the  control  wire  is  connected  in  a  manner 
similar  to  the  indication  and  control  positions.  When  lever  4 
is  reversed,  current  flows  through  the  control  wire  to  W,  to  the 
main  common  battery,  and  circuit-breaker,  G4,  thus  clearing  the 
semaphore;  G4  then  opening,  cutting  in  R  (and  W,  which  is  in 
series  with  it,  although  now  having  but  little  magnetizing  effect) 
which  retains  the  blade  in  the  clear  position.  The  clearing  cur- 
rent is  about  6  amperes,  and  tho  retaining  current  .25  ampere. 

The  indication  current,  which  is  sent  through  the  indication 
magnet  when  the  lever  has  reached  the  normal  indication  posi- 
tion, is  not  set  up  for  any  other  purpose  than  to  release  the  lever 
and  allow  the  full  reverse  movement  to  be  made,  as  in  the  case 
of  the  high  signal,  the  reason  for  this  being  that  an  interlocking 
function  is  not  to  be  released.  When  the  lever  is  moved  back  to 
normal,  R  is  open-circuited,  and  the  blade  moves  to  danger,  thus 
closing  the  circuit-breaker,  D,  and  connecting  the  main  common 
line  to  the  indication  line.  A  latch  releasing  current  then  flows 
through  74,  because  the  latter  has  been  connected  to  the  indica- 
tion line  by  the  movement  of  the  lever  to  normal. 

The  indication  common  is  not  connected  to  the  main  common 
at  the  cabin;  but  is  run  out  to  a  point  where  the  effects  of  voltage 
drop  in  the  main  common,  due  to  the  heavy  current  taken  by 
the  motors,  etc.,  will  be  at  a  minimum.  Should  this  line  be  near 
the  battery,  the  drop  in  potential  would  have  a  tendency  to 
cause  a  current  flow  back  over  the  indication  lines  of  the 
levers  not  being  operated,  and  might  open  the  safety  cut-out 


ALL-ELECTRIC  INTERLOCKING  193 

(to  be  described)  when  not  required,  resulting  in  considerable 
annoyance. 

This  cut-out  is  provided  to  eliminate  the  evil  effects  resulting 
from  crosses  between  any  of  the  various  wires.  J  and  K  are 
two  switches  connected  respectively  to  the  indication  and  opera- 
ting buses,  being  normally  held  open  by  a  spring,  and  closed  by 
current  in  the  coil,  C.  When  K  is  open,  it  cuts  the  battery  off 
from  all  functions,  while  J  opens  all  of  the  indication  circuits. 
Coil  C,  which  is  of  high  resistance,  is  connected  across  the  battery 
through  the  main  and  indication  common  lines.  H  is  a  low- 
resistance  coil,  wound  differentially  with  respect  to  C,  so  that 
the  greater  the  current  in  H  in  a  given  direction,  the  greater  the 
opposition  to  the  flux  of  C,  and  consequently  the  less  the  pull  on 
the  armature.  H  is  in  series  with  the  indication  common,  so 
that  all  indication  currents  must  pass  through  it,  these  currents 
moving  in  the  direction  of  the  arrows,  and  assisting  C  to  main- 
tain the  contacts  at  K  and  J  closed.  Any  current  flowing  from 
the  positive  side  of  the  battery  through  H,  due  to  a  cross,  will 
pass  in  the  opposite  direction  to  the  arrows,  and  consequently 
tend  to  neutralize  the  flux  set  up  by  C,  and  open  the  cut-out,  as 
the  indication  common,  to  which  H  is  permanently  connected, 
is  on  the  negative  side  of  the  battery.  All  wires  connected  to 
the  interlocking  machine  which  are  functionally  operative  are 
connected  to  the  negative  battery  terminal  through  the  indica- 
tion bus,  J,  H,  indication,  and  main  common;  hence,  current 
passing  from  any  line-wire  to  these  will  set  up  a  current  which 
produces  a  flux  in  opposition  to  C  and  thus  opens  K  and  J.  H 
has  a  low  resistance,  hence  the  greatest  percentage  of  the  current 
resulting  from  a  cross  will  flow  through  it,  and  if  this  current  be 
of  sufficient  strength  to  cause  rotation  of  a  motor  armature,  it 
will  certainly  open  the  cut-out. 

In  Fig  176  a  portion  of  a  standard  all-electric  interlocking 
machine  is  shown.  A  rear  view,  showing  the  fuse  and  terminal 
board,  is  at  1 ;  2  is  a  typical  section,  and  3  a  partial  front  view 
of  the  locking.  Besides  a  supporting  frame,  there  is  a  terminal 
board,  A,  the  controllers,  C,  levers  D,  lever  guides  E,  locking  G, 
case  H,  and  indication  and  safety  magnets,  /  and  S.  The  case 
is  provided  with  glass  doors,  for  ready  inspection  and  repairs, 
and  the  fuse  board  contains  all  fuses,  buses,  terminal  posts  and 
connections.  The  upper  bus  is  the  switch  operating,  the  lower 


194 


AUTOMATIC  BLOCK  SIGNALS 


the  signal  operating,  and  the  central  is  the  common  indication 
bus.     B  is  an  indication  selector,  which  is  used  only  on  switch 


levers,  consisting  of  electromagnets    operated  by  the  working 
current,  moving  an  armature  in  one  direction  when  the  switch 


ALL-ELECTRIC  INTERLOCKING 


195 


lever  is  normal,  and  in  the  other  direction  when  at  reverse.  It 
closes  the  indication  circuit  corresponding  to  the  lever  position, 
leaving  the  other  open. 


In  Fig.  177  the  appurtenances  directly  common  to  the  levers 
and  their  relation  are  shown.  A  shows  a  lever  entirely  in,  and 
B  the  same  four-fifths  out.  D  is  held  in  the  guides,  E,  by  the 
bars,  F,  and  is  provided  with  a  slot,  U,  which  imparts  variable 


196  AUTOMATIC  BLOCK  SIGNALS 

motion  to  the  tappet  bar,  7,  the  respective  positions  being 
numbered  1  to  5.  The  moving  contact  block,  Z,  receives  motion 
from  D  by  the  rod,  W .  I  and  S  are  the  indication  and  safety 
magnets  respectively,  and  impart  motion  to  rod  R  through  the 
armature,  T.  X  and  Y  are  stationary  contacts  connected 
to  the  various  functions,  as  shown  in  the  diagram,  Fig.  175. 
R  engages  with  P,  which  is  held  down  by  the  spring,  0,  the 
latter  also  acting  against  the  pivoted  latch,  L. 

The  raising  of  the  tappet  bar,  by  the  movement  from  1  to  2, 
locks  all  the  conflicting  levers,  the  projection,  M,  then  striking  K, 
and  tilting  the  latch,  L,  to  a  nearly  horizontal  position,  causing  J 
to  be  struck  by  Q,  thus  retaining  the  lever.  When  moving 
from  2  to  3,  Q  also  meshes  with  the  teeth  on  N,  thus  causing  the 
latter  to  rock  about  its  axis,  and  by  throwing  dog  P  into  engage- 
ment with  L,  locking  the  latter,  as  at  B.  From  3  to  4,  N  con- 
tinues its  revolution,  being  stopped  by  Q  striking  J.  Here 
an  indication  current  passes  through  7,  releasing  L  by  rea- 
son of  R  striking  P,  allowing  the  motion  from  4  to  5  to  take 
place,  thus  unlocking  the  unconflicting  levers  by  the  upward 
motion  of  V.  Hence,  D  will  be  immovable  when  conflicting 
routes  are  set  up,  and  cannot  move  from  4  to  5  without  an 
indication;  while  if  it  is  moved  to  or  beyond  3  it  cannot  pass 
4  nor  return  to  1  without  an  indication,  which  will  not  occur 
unless  the  function  controlled  is  locked  in  the  position  corre- 
sponding to  that  of  the  lever. 

The  switch  and  lock  movement  for  a  left-hand  slip  switch  is 
shown  in  Fig.  178,  and  consists  of  the  motor,  A,  and  connecting 
shaft  B,  pole-changer  C,  gear  frame  F,  driving  rod  G,  lock 
movement  H,  and  cover  L.  The  motor  is  of  enclosed  and 
weatherproof  construction,  and  operates  the  entire  arrange- 
ment. The  gear  mechanism,  F,  reduces  the  speed  of  the  motor 
armature  for  the  required  slow  movement  of  the  detector  bar 
and  switch,  and  disengages  the  motor  after  the  full  switch 
movement  has  taken  place.  This  latter  is  effected  by  the  cam, 
D,  which  is  on  the  same  shaft  as  the  main  gea,r,  by  the  clutch 
shifter,  V  (which  allows  the  shaft  to  revolve  without  affecting 
the  pinion),  and  by  toothed  clutches,  not  detailed.  Unless 
the  pinion  engages  with  one  of  the  clutches,  it  is  loose  on  the 
shaft,  so  that  when  the  stroke  is  completed  the  clutch  is  moved 
transversely  by  a  shifting-cam  on  the  main  gear,  after  which 


ALL-ELECTRIC  INTERLOCKING 


197 


the  indication  is  given.  The  main  gear-pin,  E,  moves  the  lock 
plunger,  detector  bar,  and  switch,  through  the  rod,  G,  and  crank 
cam,  D.  The  lock  movement,  H,  directly  operates,  the  pole 


changer,  detector  bar,  U,  and  lock  plunger.  G  throws  R, 
and  consequently  S  and  T}  so  that  the  switch  cannot  be  thrown 
if  a  train  be  passing  it.  C  is  moved  through  the  medium  of 


198 


AUTOMATIC  BLOCK  SIGNALS 


the  pole-changer  movement,  I,  after  the  lock  rod,  M,  is  held  by 
the  lock  plunger.  The  pole  changer  moves  in  one  direction 
when  the  switch  is  moved  normal  and  in  the  opposite  direction 
at  reverse,  with  results  already  shown  diagrammatically. 

The  operation  of  the  switch  movement  is  as  follows:  When 
the  switch  lever  has  been  thrown,  and  the  motor  connected 
to  the  battery,  the  armature  drives  the  main  gear  through 


FIG.  179 


one  revolution.  At  the  first  part  of  its  revolution  the  lock 
bolt  is  released,  and  the  detector  bar  raised.  The  pin,  E}  then 
strikes  the  outer  end  of  the  pivoted  cam,  D,  thus  throwing 
the  switch,  this  taking  approximately  one-third  of  a  revolution. 
The  remaining  third  of  the  revolution  results  in  the  lowering 
of  the  detector  bar,  and  setting  of  the  lock  bolt,  the  pole  changer 
being  thrown  as  soon  as  the  plunger  passes  through  the  lock 
rod,  the  motor  disengaged,  and  the  indication  given. 


ALL-ELECTRIC  INTERLOCKING 


199 


The  reversible  pole-changer  mechanism,  shown  in  outline 
and  connection  at  the  switch  machine  and  designated  by  P 
in  the  diagram,  is  illustrated  in  plan  and  elevation  in  Fig.  179. 
Rod  W  is  connected  mechanically  to  the  lock  bolt,  and  operates 
the  movable  contacts,  which  engage  the  fixed  contact-fingers 
N.  V  is  a  control  drum,  acting  as  a  circuit- breaker,  which  is 
operated  by  the  shaft  (shown  dotted)  carrying  the  main  gear 
and  cam  so  that  the  magnets,  M,  are  open-circuited  when  the 
switch  is  home  and  locked.  The  movable  cores,  to  which  the 
moving  contact  blocks  are  secured,  are  under  the  control  of 
the  magnets  when  the  switch  is  to  be  thrown.  These  magnets 
are  shown  at  M  and  Mf  in  the  circuit  diagram  also. 

A  Taylor  switchbox  (or  ground  selector)  is  shown  in  Fig. 
180.  The  movement  of  the  switch  rails  throws  the  link,  C, 


thereby  bringing  the  movable  contact  members,  5,  into  con- 
nection with  the  row  of  stationary  clips,  D,  closing  the  desired 
circuits.  When  the  switch  is  thrown  in  the  other  direction  the 
contact  strips,  A,  engage  with  a  similar  row  of  contacts  on  the 
opposite  side  of  the  box.  This  device  is  used  for  any  appli- 
cation of  functions  depending  upon  switch  or  other  movement 
for  their  control. 

Fig.  181  shows  a  Taylor  hook  selector,  suitable  for  fastening 
to  a  signal  pole  and  controlling  a  semaphore.  B  is  the  counter- 
weighted  lever,  which  normally  has  no  connection  with  lever  D. 
The  latter  is  keyed  to  the  shaft,  F,  while  B  moves  about  F  as 
a  center  merely.  When  the  electromagnet  is  energized,  the 
armature,  E,  is  raised,  causing  hook  C  to  be  thrown  directly  in 
the  path  of  a  cross  piece,  fastened  to  5,  so  that  movement  of 
the  latter  cannot  occur  without  D  being  moved.  Hence, 
when  B  is  pulled  in  the  direction  of  the  arrow  by  the  motor, 


200 


AUTOMATIC  BLOCK  SIGNALS 


the  signal  will  be  cleared,  if  A  is  energized.  When  the  inter- 
locking lever  for  the  signal  is  thrown,  current  passes  through 
the  proper  selector  magnet,  through  the  motor  and  circuit 


FIG.  181 

breakers.  This  clears  the  signal,  the  indication  being  given  in 
the  usual  manner.  From  two  to  five  arms  may  thus  be  oper- 
ated, and  if  ground  selectors  are  used,  but  one  interlocking  lever 
is  required. 


CHAPTER  XV. 
THREE-POSITION    SIGNALS. 

THREE-POSITION  semaphores  eliminate  the  distant  blade  and 
still  give  an  indication  of  the  condition  of  the  distant  block. 
This  is  accomplished  by  using  three  distinct  positions  of  the 
semaphore:  the  all-clear  being  vertical;  the  caution  diagonal; 
and  the  stop  position  horizontal,  or  nearly  so.  The  control 
and  operation  may  be  effected  by  either  line  or  track  circuits, 


to  charging  wire 


FIG.  182 

the  former  being  first  described.  Considering  three  consecutive 
signals,  No.  3  being  occupied,  1  and  3  will  be  controlled  by  the 
track  circuits  in  the  blocks  they  protect,  while  2  will  be  con- 
trolled by  line  wires  from  3. 

Figs.  182  and  183  show  the  consecutive  circuits  employed  in 
the  Grafton  arrangement  of  such  signals.  Fig.  182  gives  the 
connections  at  the  first  signal  considered;  the  semaphore,  17, 
being  operated  by  a  motor,  19,  of  about  .1  horse  power,  its  posi- 

201 


202 


AUTOMATIC  BLOCK  SIGNALS 


tion  and  movement  being  governed  by  the  slot  instrument,  18. 
The  armature  contacts,  13,  of  the  track  relay,  10,  are  in  series 
with  the  cut-out,  22  (operated  by  the  motion  of  the  sig- 
nal mechanism),  and  one  side  of  the  main  or  storage  battery,  7, 
the  latter  being  located  at  the  signal,  and  charged  by  feed  wires 
running  on  poles  from  a  central  generating  plant,  one  side  of 
this  battery  being  connected  to  the  common  line,  23.  If  the 
contacts,  6,  are  closed,  a  current  will  pass  through  18,  which 
locks  the  signal  and  holds  it  in  the  clear  position  shown. 
Should  10  be  deenergized,  however,  by  reason  of  16  being 


FIG.  183 

short-circuited  by  a  train  in  the  section,  18  will  be  released  and 
17  will  return  to  the  stop  position.  Circuit-breaker  4  is  closed 
when  the  signal  is  in  either  the  stop  or  the  caution  position,  but 
is  opened  in  the  clear  position;  while  5  is  closed  only  in  the  stop 
position,  and  6  closed  in  the  clear  and  caution  positions.  The 
three-position  relay,  1,  is  in  series  with  the  line  wires,  and  has  two 
armatures,  2  and  3;  the  former  shunting  the  circuit- breakers, 
and  the  latter  connecting  the  motor  to  one  side  of  the  battery 
through  4,  22,  and  13.  If  the  wires,  15  or  14  (Fig.  183),  should 
be  broken  it  is  evident  that  7  would  be  continually  passing  a 
heavy  current.  To  guard  against  such  an  occurrence,  the  cir- 
cuit opener,  22,  operated  by  the  signal  mechanism,  is  provided. 


THREE-POSITION  SIGNALS 


203 


The  armatures,  11, 12,  and  13,  of  relays  8,  9,  and  10,  are  in  series 
with  this  device. 

The  special  parts  of  the  signal  mechanism  are  shown  in  Fig. 
184.  The  semaphore  is  connected  to  the  rod  which  is  fastened 
to  the  sleeve,  F,  the  accessories  being  secured  to  the  latter,  and 
move  with  it  when  the  semaphore  is  cleared.  The  rod,  M,  is 
operated  through  a  train  of  gears  by  the  electric  motor,  there 
being  three  stationary  positions. 
B  is  the  slot  magnet,  whose 
armature  affects  the  position  of 
the  lock  block,  L,  through  the 
toggle  arrangement,  C-D-K.  A 
is  a  dashpot,  whose  piston  is 
stationary,  it  being  required  to 
prevent  spasmodic  movements 
of  the  moving  system,  and  pre- 
vent the  inertia  of  the  latter 
from  injuring  the  mechanism. 
N  and  J  are  latches  which  engage 
with  F  at  its  various  positions 
and  relieve  the  motor  and  gearing 
of  the  weight  of  the  apparatus 
when  at  rest. 

When  B  is  energized,  L  is 
forced  into  engagement  with  a 
recess  upon  the  upper  end  of 
M,  so  that  motion  of  the  latter 
results  in  motion  of  the  former, 
their  tendency  being  to  disen- 
gage. The  circuit-breakers  not 
shown  are  operated  by  an  ex- 
tension of  the  sleeve,  F,  while  /  is  the  armature  extension  of 
a  catch  magnet,  which,  when  deenergized,  prevents  F  from  mov- 
ing upward  by  the  hooked  end  of  the  armature  being  forced 
into  the  notches,  0,  by  the  spring,  H.  The  operation  of  the  signal 
should  be  readily  perceived  from  the  above  description,  a  rather 
complicated  application  in  conjunction  with  semi-automatic 
signals  being  now  taken  up. 

In  Figs.  185  and  186,  the  connections  of  two  automatic  three- 
position  signals  on  double  track,  and  their  relation  to  mechani- 


/    L 


FIG.  184 


204  AUTOMATIC  BLOCK  SIGNALS 

cal  semaphores,  moved  by  levers  from  a  cabin  at  a  junction, 
are  shown.  Both  2  and  4  are  electrically  operated,  but  are  also 
under  the  control  of  the  signalman;  while  1  and  2  are  entirely 
automatic.  In  order  to  trace  out  the  connections  most  expe- 
ditiously,  Figs.  182  and  183  should  again  be  consulted.  Both 
diagrams  are  similarly  arranged,  and  are  connected  by  the  line 
wires,  1  to  7. 

At  10  in  Fig.  185,  the  circuits  at  signal  1  are  shown, 
the  remainder  of  the  figure  being  devoted  to  the  connections  of 
2  and  the  interlocking  functions.  The  circuit- breakers,  16  and 
17,  are  opened  when  the  semaphore  of  1  is  moving  to  the  clear 
position,  while  18  is  closed,the  three-position  relay,  19,  controlling 
signal  1,  current  being  derived  from  the  main  battery,  11.  Cir- 
cuit-breakers 22,  23,  and  24  are  similar  in  function  and  operation 
to  those  operated  by  1,  while  25  is  in  series  with  one  of  the  con- 
tacts of  the  circuit  controller,  14.  The  latter  is  operated  by  the 
lever  which  throws  4  of  Fig.  186  to  the  clear  position,  at  which 
time  the  breaking  device,  31,  is  closed.  This  effects  a  cau- 
tionary indication  through  the  distant  line  wire. 

The  lock  magnet,  27,  is  for  the  purpose  of  securing  the  lever 
for  4  in  the  stop  position,  unless  it  is  energized  by  way  of  the 
common  and  No.  4  line  wires,  through  13  and  the  first  of  the  set 
of  contacts  32.  When  the  lever  of  4  is  reversed,  the  lever  relay, 
28,  is  energized  and  acts  as  a  controlled  function;  the  stick  relay, 
38,  through  its  lower  armature,  being  interposed  for  accom- 
plishing this  purpose.  The  latter  must  be  energized  before  the 
signal  can  again  be  cleared. 

In  tracing  up  the  circuits  it  should  be  remembered  that  2 
is  controlled  in  a  manner  similar  to  4,  and  that  while  its  con- 
nections are  shown,  only  those  of  the  latter  are  described. 
As  the  latch  of  the  lever  for  4  is  lifted  the  circuit  controller,  13, 
is  shifted,  so  that  the  stick  relay,  15,  is  connected  through  con- 
tacts, 36,  and  the  upper  armature  of  15  and  its  coils,  line-wire  4, 
and  the  storage  battery.  The  lever  relay,  28,  has  been  closed 
through  the  storage  battery,  armature  37  of  the  control  relay, 
35  (of  signal  4),  line  7,  36,  lower  armature  of  15,  line  5,  lever 
relay  33,  line  3,  and  to  the  battery.  When  13  is  not  shifted, 
we  have  from  the  battery,  37,  line  7,  36,  upper  armature  of 
15,  15,  line  4  to  battery. 

As  33  is  on  closed  circuit  when  the  signal  latch  is  raised,  it 


THREE-POSITION  SIGNALS 


205 


206 


AUTOMATIC  BLOCK  SIGNALS 


performs  the  office  of  a  track  relay,  the  motor  and  other  circuit 
being  closed  by  its  armature,  thus  allowing  the  semaphore  to 
be  cleared.  With  a  train  between  1  and  4,  track  relay  35  is 
short-circuited,  which  open-circuits  33  and  15,  thus  causing  4 


-a 


Jl^ 
if  I 


to  move  to  the  stop  position.  When  the  lever  of  4  is  put  into 
its  normal  position,  15  will  be  energized  by  reason  of  36  being 
connected  to  39  (13  and  14  are  supposed  to  move  vertically). 
It  will  be  evident  that  these  semi-automatic  signals  are  thus 


THREE-POSITION  SIGNALS  207 

returned  electrically  to  the  stop  position,  and  cleared 
mechanically. 

When  33  is  energized,  4  cannot  be  cleared  unless  the  block 
ahead  is  clear,  because  of  the  track  relay  introduced;  which  is 
also  the  case  in  the  automatic  control  of  signal  1.  The  lever 
of  4  is  locked  in  its  stop  position  by  the  deenergization  of  the 
lock  magnet,  27;  hence  the  latter  must  have  its  circuit  to  battery 
closed  through  39,  the  first  left-hand  set  of  the  contacts,  32, 
line  6,  battery,  and  line  4.  The  first  set  of  contacts  at  32  will 
not  be  closed,  however,  unless  4  is  in  the  stop  position. 

Slot  circuit-closers  32  are  operated  in  a  manner  similar  to 
the  three-position  contactors  that  have  been  described.  With 
a  clear  track,  the  signalman  must  first  clear  4  before  a  train  can 
enter  the  block.  The  unlatching  moves  13,  and  simultaneously 
31,  thereby  throwing  the  signal,  by  sending  a  current  from  the 
battery  through  the  motor  circuit.  The  circuit  closer,  31,  is 
similar  to  12,  while  29  and  42  are  three-position  relays.  The 
contractors,  30,  are  operated  by  signal  3;  and  14  is  a  circuit  con- 
troller, similar  to  13,  operated  by  movement  of  2.  The  respec- 
tive signal  slots  are  bv  62,  etc.,  the  track  relays,  av  etc. 

In  Fig.  187,  the  connections  of  three  consecutive  G.  E.  three- 
position  signals,  75,  85,  and  95,  appear.  Two  line  wires,  1  and 
2,  interconnect  the  various  signals,  these  being  in  series  with 
the  three-position  relays,  R.  The  contacts  of  the  latter  are 
closed  when  the  semaphore  is  in  the  clear  and  danger  positions, 
and  open  when  in  the  caution  position.  The  controller,  A,  is 
an  arrangement  with  movable  sectors  and  stationary  contacts; 
and  rotates  in  an  opposite  sense  (in  the  diagram)  to  the  sema- 
phore. The  lock  magnet,  L,  holds  the  semaphore  in  position, 
and  the  clutch  magnet,  C,  in  series  with  the  motor,  M ,  engages 
the  semaphore  operating  gear  at  its  various  positions  of  rest. 

When  the  semaphore  is  at  clear,  7  is  connected  to  8,  and  the 
lock-magnet  and  three-position  relay  (at  65)  are  in  multiple, 
being  energized  by  the  power  battery,  P,  at  75.  The  lock  mag- 
net holds  the  semaphore  at  clear,  and  opposes  the  tendency  of 
gravity  to  move  it  to  the  stop  position.  As  R  is  energized,  the 
current  to  the  lock  magnet,  L,  is  in  series  with  its  armature. 

With  the  semaphore  at  caution,  6  and  7  and  4  and  5  are  con- 
nected. The  three-position  relay,  R,  at  85  is  deenergized,  since 
the  track  battery,  T,  at  95,  is  short-circuited.  Current  thus 


208 


AUTOMATIC  BLOCK  SIGNALS 


THREE-POSITION  SIGNALS  209 

passes  through  R  (at  75)  and  the  lock  magnet  in  parallel,  the 
motor,  M,  being  out  of  circuit  at  this  moment. 

When  the  semaphore  is  at  danger,  as  at  95,  the  track  relay,  0, 
is  short-circuited,  thus  cutting  the  motor  out  of  circuit  with  the 
power  battery.  The  three-position  lock  and  clutch  magnets 
are  thereby  deenergized,  and  the  semaphore  is  acted  upon  only 
by  gravity.  It  should  be  remembered  that  all  movements 
toward  full  clear  are  performed  by  the  motor,  and  all  toward 
danger  by  gravity.  Thus  the  return  from  clear  to  caution  is 
effected  by  gravity  under  the  control  of  the  lock  magnet. 

In  Fig.  188  a  later  modification  of  the  above  is  shown.  The 
power  battery,  P,  in  this  case  is  disconnected  from  the  motor 
circuit  by  a  quadruple  break  as  are  also  the  stationary  con- 
tacts, 4  and  7,  of  the  controller.  These  contacts  carry  the  heavy 
working  current,  the  actual  construction  being  shown  in  Fig.  190. 

One  form  of  G.  E.  top  post,  automatic,  three-position  signal, 
such  as  is  used  in  connection  with  signal  bridges,  is  illustrated 
hi  Fig.  189.  The  glass  spectacles  are  removed,  the,  semaphore 
being  in  the  caution  position.  The  return  to  stop  is  assured  (by 
reason  of  a  preponderance  of  weight  on  the  left  side)  after  the 
lock  magnet  has  released. 

The  internal  mechanism  of  the  top  post  three-position  signal 
is  shown  in  Fig.  190,  the  doors  of  the  housing  being  thrown 
open.  The  small  series-wound  motor,  M,  drives  the  main  gear, 
G,  which  is  indirectly  connected  to  the  semaphore  shaft. 
Secured  to  this  same  shaft  are  the  contact  sectors  of  the  con- 
troller, S,  which  engage  with  fixed  clips  during  rotation.  An 
intermediate  shaft  gear  and  pinion  exist  to  further  decrease 
the  motor  speed.  D  is  a  dashpot,  whose  piston  rod  is  connected 
to  a  crank,  carried  by  the  semaphore  rock  shaft,  to  prevent 
injury  to  the  parts  when  the  blade  returns  to  stop.  C  is  the 
lock  and  L  the  clutch  magnet,  whose  connections  were  shown 
in  Fig.  187.  The  stationary  contacts  of  the  controller  are  con- 
nected to  the  track-relay  armatures,  lock  and  clutch  magnets, 
battery  and  lines,  in  the  order  shown  in  the  latter  circuit  diagram. 
The  clutch  magnet  operates  a  toggle  clamp  which  holds  the 
semaphore  in  its  proper  position. 

The  lock  magnet  is  in  circuit  when  the  blade  is  at  clear  and 
caution,  but  not  when  in  the  stop  position;  the  clutch  magnet 
being  in  circuit  whenever  the  motor  is,  since  it  is  in  series  with 


210 


AUTOMATIC  BLOCK  SIGNALS 


THREE-POSITION  SIGNALS 


211 


the  latter.    The  circuit  is  broken  by  a  spring  action  quick  break, 
so  that  burning  of  the  contacts  will  be  minimized. 

A  later  development  of  the  above  three-position  (normal  clear) 
operating  structure,  appears  in  Fig.  191.  The  14-volt  series 
motor,  A,  drives  the  train  of  gears  and  pinions,  C,  D,  E,  F, 
thereby  transmitting  a  rotary  movement  to  the  clutch  wheel,  H, 
which  is  free  to  move  on  the  semaphore  shaft,  J.  The  inner  face 


FIG.  189 

of  this  clutch  gear  contains  a  plurality  of  V-shaped  bosses,  B, 
with  which  the  clutch  structure,  K,  engages,  when  the  operating 
magnets,  M-M',  are  energized.  These  magnets,  with  their 
armature  and  toggle  levers,  are  mounted  on  a  sector  frame,  S, 
which  is  rigidly  keyed  to  the  shaft,  J,  and  thus  gives  motion  to 
the  semaphore,  the  latter  being  attached  at  Q.  The  motor  and 
clutch  magnets,  as  shown  in  the  diagram,  are  connected  in 
series,  so  that  when  the  motor  is  operative,  these  coils  are  ener- 
thus  causing  the  toggle  levers  to  force  the  working  end 


212  AUTOMATIC  BLOCK  SIGNALS 

into  engagement  with  the  bosses  on  the  clutch  wheel,  which  is 
then  revolved  in  the  direction  of  the  arrow  by  the  motor, 
thereby  throwing  the  semaphore  to  the  caution  or  clear  direc- 
tion. This  locking  sector,  8,  mounted  directly  on  the  shaft,  J, 
is  provided  with  bosses  (not  evident  in  the  position  given) 


FIG.  190 

which  engage  with,  and  are  securely  held  by,  the  toggle  levers 
operated  by  the  magnets,  N-  N',  at  the  caution  and  clear  posi- 
tions. By  the  action  of  the  control  contacts,  a,  b  (and  four 
others  at  the  rear  of  P),  and  the  segments,  U  and  U',  the  motor 
is  thrown  in  and  out  of  circuit.  In  the  caution  position  N-N' 
is  energized  and  the  lock  toggles  (counterweighted  at  0),  engage 
with  the  boss  on  the  locking  sector,  thus  holding  the  semaphore 


THREE-POSITION  SIGNALS 


213 


at  the  45°  position.  With  the  track  circuit  justifying  a  clear 
indication  (which  is  normal);  a  similar  scheme  of  connections 
obtains,  with  the  same  sequence. 

The  contact  segments,  U,  Uf,  and  C7",  effect  the  proper  varia- 
tion of  interconnection  with  the  contact  fingers,  a,  6,  c,  d,  etc., 


FIG.  191 

and  are  mounted  on  the  shaft  sleeve,  P  (keyed  to  J),  carrying 
the  plunger  of  the  oil  filled  dashpot,  DP,  and  insulated  by  the 
moulded  collars,  n,  n',  and  n".  The  remaining  connections  and 
especially  those  made  by  the  fingers  and  posts  hidden  from 
view,  are  effected  as  in  the  diagram  and  preceding  mechanism. 
An  additional  adjustable  control  segment,  U",  and  fingers,  c  and 


214  AUTOMATIC  BLOCK  SIGNALS 

dj  constitute  an  auxiliary  control  feature,  for  purposes  of  indica- 
tion at  a  block  tower  or  similarly  appointed  location. 

By  arranging  the  mechanism  adjacent  to  the  semaphore,  with 
the  rock  shaft  of  the  latter  driven  directly  by  the  gearing,  a 
remarkably  self-contained  unit  is  assured.  This,  in  combina- 
tion with  the  three-position  arrangement,  marks  a  step  for- 
ward in  the  standardization  of  automatic  signals.  The  energy 
taken  by  the  motor  is  also  greatly  reduced,  owing  to  the  absence 
of  clumsy  connections  and  accessories. 

The  three-position  Hall  electrorgas  signal  employs  two  cylin- 
ders which  are  connected  to  the  single  signal  rod  by  a  walking 
beam.  When  the  home  clears,  the  beam  is  lifted  at  one  end, 
the  signal  rod  moving  half  its  distance,  the  fulcrum  being  at  the 
distant  cylinder.  When  the  latter  clears,  the  end  at  the  home 
cylinder  is  the  fulcrum,  the  rod  being  thus  forced  to  complete 
its  stroke.  About  three  seconds  are  required  for  clearing  such 
a  semaphore,  a  single  cylinder  moving  its  entire  stroke  in  from 
one  to  two  seconds. 


CHAPTER  XVI. 
ELECTRIC  RAILWAY  SYSTEMS. 

ELECTRIC  railway  signals  have  not  as  yet  reached  the 
perfection  that  steam  road  devices  approach,  owing  to  their 
more  recent  application,  and  the  inherent  difficulties  obtain- 
ing in  such  systems  which  do  not  have  to  be  considered  in  the 
latter  case.  Chief  among  these  is  the  leakage  current  neces- 
sarily the  concomitant  of  a  grounded  system  in  which  heavy 
currents  at  high  voltage  are  employed.  This  leakage  is  so 
great  that  ordinary  battery  relays  become  useless.  An  advan- 
tage, which,  however,  can  be  over-estimated,  is  the  power 
circuit  current  that  can  be  drawn  in  any  quantity  at  every 
point  on  the  right  of  way.  Nearly  all  signals  applied  to  electric 
lines  employ  a  contact  device  operated  directly  or  indirectly  by 
the  trolley  wheel,  third-rail  shoe,  or  other  part  of  the  moving  car. 

On  a  grounded  return  direct-current  street  railway  system, 
or  on  a  steam  road  which  is  crossed  by  or  interconnected 
through  ground  pipes  or  bridges  with  such  a  system,  it  some- 
times becomes  advantageous  to  use  a  signaling  scheme  which 
will  not  respond  to  direct  current.  The  working  circuits  may 
be  of  direct  current,  this  latter  either  obtained  from  batteries 
or  the  power  lines;  but  the  control  circuits  carry  only  alterna- 
ting current.  Such  an  arrangement  is  represented  generically  in 
Fig.  192,  the  circuits  having  two  insulated  components,  one  con- 
taining the  secondary,  S,  of  a  small  transformer  or  converter,  and 
the  other  the  primary  coil,  P.  The  track  is  connected  to  an 
alternating-current  supply,  the  special  laminated  magnetic  circuit 
relay,  R,  governing  the  elements  for  either  a  normal  clear  or  a 
normal  danger  system.  A  direct  current,  whether  by  leakage  or 
grounded  connection,  flowing  through  the  primary,  cannot  induce 
a  current  in  the  secondary  or,  consequently,  operate  the  signal. 

In  the  New  York  Subway,  but  one  track  is  divided  into  insu- 
lated sections,  the  signals,  lamps,  and  relays  being  operated  by 
alternating  current,  these  relays  having  vanes  instead  of  arma- 

215 


216 


AUTOMATIC  BLOCK  SIGNALS 


tures  to  close  the  contacts.  Several  other  such  systems  have 
been  devised  and  applied,  but  not  to  an  extent  that  would 
warrant  their  description  herein. 

On  an  alternating-current  road,  the  relays  can  be  made  of 
high  ohmic  impedance,  so  that  an  alternating  current  cannot 
set  up  sufficient  current  in  the  coils  to  lift  the  armature.  Direct 
current  is  of  course  used  in  both  supply  and  control  circuits, 
since  the  opposing  inductance  of  the  relays  is  but  momentary, 
and  manifested  only  when  a  change  in  current  strength  occurs. 

Fig.  193  is  a  diagram  showing  the  circuit  arrangement  used 
in  the  Uni  direct-current  system.  The  trolley  wheel,  T,  operates 
a  special  switch,  L,  and  closes  a  circuit  according  to  the  direction 
of  motion.  7  is  a  lightning  arrester  in  series  with  the  perma- 
nent feed-wire,  M .  The  latter  is  connected  to  a  red  lamp,  F, 
the  locking  electromagnet,  A,  the  contacts,  E,  operated  by  B, 
the  contact,  D,  lightning  arrester  K,  lighting  line-wire  R,  and 
to  ground,  through  similar  apparatus  at  N.  B  and  C  are  the 


to  signal 


alternating  current  \supply 
FIG.  192 

lighting  magnets,  since  when  they  are  energized  the  lamps 
are  lighted.  These  are  alternately  excited,  the  cores  acting 
upon  a  walking  beam.  In  the  position  shown,  the  green  lamp, 
G,  is  energized,  while  in  the  opposite  position,  F  will  be  in 
circuit.  The  extinguishing  line-wire,  S,  is  in  series  with  B, 
through  the  lightning  arrester,  J,  and  the  trolley  switch,  L,  or 
the  switch  contacts,  0,  operated  by  C.  H  is  a  resistance 
interposed  in  the  power  circuit  to  keep  the  current  down  to 
the  required  figure.  A  operates  the  contacts,  P,  and  locks 
the  arrangement,  preventing  interference. 


ELECTRIC  RAILWAY  SYSTEMS 


217 


When  a.  car  enters  the  block,  the  automatic  switch  is  struck 
by  the  trolley,  thus  lighting  the  green  lamp  at  the  home  end  of 
the  block,  at  the  same  time  lighting  the  red  lamp  at  the  distant 
end;  the  latter  being  in  series  with  the  former.  When  the  car 
reaches  the  trolley  switch  at  the  leaving  or  distant  end  of  the 
block,  both  lamps  are  extinguished.  The  block  is  thus  unoccu- 
pied when  both  lamps  are  out,  and  occupied  when  either  red 
lamp  is  in  circuit.  Since  the  arrangement  is  double  acting, 
this  applies  to  cars  entering  either  section.  The  current  carried 
under  any  condition  is  one-half  ampere. 

trolley  wire  


FIG.  193 

Unless  a  car  receives  a  green  signal  on  approaching  a  block, 
that  block  is  in  a  dangerous  condition.  A  car  following  one 
already  occupying  the  block  does  not  affect  the  signal  circuits 
set  up  by  the  former,  and  a  visual  indication  will  not  be  given 
to  either  should  a  lamp  burn  out.  The  latter  is  a  remote  possi- 
bility, since  they  are  renewed  monthly. 

The  single- wire  circuit  arrangement  used  in  conjunction  with 
the  Eureka  system,  is  shown  in  Fig.  194.  G  is  a  contact  maker, 
consisting  of  steel  combs  having  contact  teeth,  connected  on 
one  side  to  the  feed  wire  and  to  the  rail  or  ground  through  the 
electromagnet,  M,  and  the  resistance,  R.  The  lamps,  L,  are 


218 


AUTOMATIC  BLOCK  SIGNALS 


shunted  by  the  resistances,  S,  so  that  should  any  burn  out  the 
remainder  will  still  give  visual  indication.  M  operates  a  con- 
tact arrangement  consisting  of  a  rotating  structure  carrying 
contact  fingers  A,  which  engage  with  contacts  P,  0,  and  N, 
according  to  the  position  of  the  mechanism.  A  similar  com- 
bination is  used  at  B.  When,  as  shown  in  the  figure,  the  lamps, 
L,  are  burning,  it  indicates  that  the  block  is  occupied.  When 
this  does  not  occur,  the  lamps  are  either  connected  to  the  feed 
wire,  or  to  ground  only.  But  one  car  at  a  time  can  thus  occupy 
a  block. 

In  the  two-wire  system,  a  diagram  of  which  is  given  in  Fig. 
195,  a  number  of  cars  can  be  in  the  block  at  the  same  time. 


Teed  wire 


FIG.  194 

The  contact  comb  in  this  case  has  three  members,  a  long  comb 
on  one  side  of  the  trolley  wire,  and  two  short  ones  on  the  opposite 
side.  The  main-current  controller,  G,  has  two  electromagnets, 
F  and  Et  which  act  independently  upon  the  rotating  member. 
When  a  car  enters  the  block,  the  current  passes  from  the  short 
comb  the  wheel  comes  first  in  contact  with,  sending  current 
through  the  setting  magnets  and  holding  the  signals  at  danger. 
One  of  the  magnets  actuates  an  automatic  switch,  so  that  the 
current  passes  through  the  same  coil  when  the  second  short 
comb  is  struck.  C  and  D  constitute  a  current-directing  relay 
whose  function,  as  above  stated,  is  to  keep  the  current  from  both 
short  combs  flowing  through  the  same  magnet,  when  the  trolley 
wheel  strikes  the  contact  maker.  When  a  car  enters  the  block 
it  switches  the  current  from  both  combs  through  the  operating 


ELECTRIC  RAILWAY  SYSTEMS 


219 


magnets,  setting  the  system  at  clanger;  and  when  the  car  leaves 
the  block  it  similarly  sets  the  system  at  safety.  This  occurs 
in  both  directions. 

Under  normal  operative  conditions,  the  circuit  of  an  empty 
block  is  grounded  at  both  ends.  This  circuit,  as  above  shown, 
consists  of  four  green  lamps,  g,  in  series  with  a  red  lamp,  r,  at 
either  end  of  the  block.  The  controller,  /,  is  similar  in  construc- 
tion to  G]  the  auxiliary  controller,  H,  being  interposed,  whose 
function  it  is  to  open  or  close  the  magnet-operating  circuit. 
Should  two  cars  enter  the  block  from  opposite  ends,  this  latter 
opens  the  circuit  automatically,  so  that  one  car  must  back  out 
of  the  block,  thereby  restoring  the  apparatus,  and  giving  the 


feed  wire 


FIG.  195 

other  car  the  right  of  way.  When  a  car  enters  an  unoccupied 
block,  H  closes  the  circuit,  so  that  when  the  car  leaves  the  block 
at  the  other  end  the  main  controller  first  energized  is  again  ener- 
gized, thus  restoring  the  circuits  to  their  normal  condition. 
This  device  may  be  dispensed  with,  but  it  makes  a  more  effective 
and  desirable  combination. 

The  United  States  system  employs  pivoted  disks  or  "  sema- 
phores "  in  addition  to  lamps,  these  semaphores  being  operated 
by  magnets.  A  mechanical  locking  device  also  secures  the 
contacts  until  released  by  the  car's  leaving  the  block.  In  Fig. 
196,  the  internal  circuits  at  each  end  of  the  block  are  shown; 
and  in  Fig.  197,  the  external  circuits  of  the  entire  block.  Since 
but  two  lamps  are  normally  in  circuit  at  the  same  time,  resist- 
ances R  are  interposed  to  keep  down  the  current.  When  a  car 
enters  the  left-hand  (or  setting)  end,  the  wheel  closes  the  right- 
hand  side  of  the  trolley  switch;  the  current  thereby  flowing 


220 


AUTOMATIC  BLOCK  SIGNALS 


through  the  magnet,  B,  line  3,  to  the  other  signal  and  ground. 
When  B  is  energized,  it  throws  over  its  contact  lever,  thus  dis- 


RCLAY 


connecting  the  ground  wire,  and  putting  the  feed  from  the 
trolley  wire  into  circuit,  the  trolley  switch  contact  opening 
immediately  after  the  car  has  passed.  The  green  lamp  is  then 


ELECTRIC  RAILWAY  SYSTEMS 


221 


illuminated  and  its  semaphore  thrown,  thus  indicating  that  the 
red  lamp  and  semaphore  have  been  set  at  the  other  end  of  the 
block.  The  remaining  contacts  closed  by  the  movement  of 
the  armature  of  B  close  a  circuit  including  the  outside  contact  of 
both  trolley  switches.  The  magnet,  A,  is  in  series  with  the  sig- 
naling circuit,  and  opens  two  non-interference  contacts  in  series 
with  the  trolley  switch,  thus  preventing  a  car  from  entering  at 
the  opposite  end  of  the  block,  locking  the  lever  of  the  magnet,  B, 
at  this  end,  making  a  normal  indication  until  the  car  passes  out 
of  this  end  of  the  block.  Line  2  and  its  connectipns  constitute 
a  releasing  circuit.  Upon  the  car  passing  out  of  the  block,  it 
operates  the  outbound  trolley  switch,  closing  the  right  hand 


SWITCHES 
-TROLLEY     W//?fN  \ 


FIG.  197 

contacts,  sending  a  current  through  C  at  this  end  of  the  block, 
thus  breaking  the  signaling  circuits  and  that  of  magnet  A  through 
the  contacts  of  the  latter's  armature ;  and  unlocking  the  armature 
of  B  by  releasing  lock  piece  F.  Since  B  is  deenergized,  the 
apparatus  is  again  in  its  normal  condition.  The  above  sequence 
of  connections  occurs  with  a  car  moving  in  either  direction. 
The  actual  arrangement  of  the  contact  carrying  members  H  and 
Kj  and  of  the  stationary  contacts,  G  and  Z),  is  not  as  shown  in 
the  figure,  where  an  attempt  is  made  only  to  show  the  principle. 
In  the  Kinsman  system,  a  remote  modification  of  which  is  used 
on  the  Boston  Elevated  and  Interborough  Rapid  Transit  Rail- 
roads (electric,  although  it  is  equally  well  adapted  to  steam  roads), 
an  automatic  train-stop  is  employed  in  conjunction  with  a  manual 
or  automatic  visual  system  in  such  a  way  that  the  control  of  the 


222  AUTOMATIC  BLOCK  SIGNALS 

train  is  taken  from  the  engineman  or  motorman  at  a  critical 
time,  so  that  it  is  not  possible  to  pass  a  danger  signal.  This 
arrangement  meets  the  demand  for  a  device  which,  independ- 
ently of  the  motorman  or  engineman,  would  set  up  a  retarding 
effect,  preventing  procedure  into  an  occupied  or  otherwise  dan- 
gerous block. 

Fig.  198  shows  the  above  applied  to  a  normal  clear  automatic 
visual  system.  The  home  and  distant  semaphore  signal,  S,  has 
its  home  control  magnet  equipped  with  an  auxiliary  armature,  w, 
which  has  a  front  and  back  contact,  and  is  in  series  with  a  switch 
box,  Ej  the  slightly  elevated  guard  or  contact  rails,  G,  and  the 
battery,  B.  These  contact  rails  are  each  about  120  feet  in  length, 
with  inwardly  curved  ends.  The  battery,  B,  is  in  two  parts;  onet 
side  having  a  voltage  of  about  5,  and  the  other  side  3.  The 
front  contact  of  m  is  connected  to  the  junction  of  these  parts, 
so  that  when  it  is  in  the  upper  position,  the  voltage  impressed 
on  the  circuit  will  be  3,  and  in  the  lower  position,  8. 

Two  contact  arms,  K,  are  fastened  to,  and  insulated  from,  the 
locomotive;  these  making  a  scraping  contact  with  the  guard 
rails.  Connected  to  these  contact  pieces  and  the  engine  or  car 
frame  is  a  circuit  containing  an  electrical  recording  device,  H, 
and  a  stop  magnet,  J,  the  latter  operating  directly  on  the  throttle 
(or  control  switch,  controller,  or  circuit  breaker  of  an  electric 
train),  or  being  so  interposed  that  it  forms  a  positive  link  between 
the  throttle  and  valve.  Simultaneously  with  the  shutting  off 
of  the  steam  or  current,  the  air  brake  is  applied. 

Returning  to  Fig.  198,  if  a  train,  represented  by  the  loco- 
motive equipment,  H-K,  be  moving  in  an  easterly  direction 
with  a  dangerous  track  (having  the  switch  A  open),  and  con- 
sequently with  the  signal  in  the  danger  or  stop  position;  as 
soon  as  the  contact  arms  strike  the  guard  rails,  a  current  passes 
from  all  of  B  through  m,  to  the  switch  box,  guard  rails,  stop- 
valve  magnet,  and  returns  through  the  frame  of  the  engine 
and  rail.  The  stop- valve  shuts  off  the  steam,  applies  the  air 
brake,  and,  by  raising  its  armature,  closes  the  circuit  of  the 
danger-recording  magnet,  HI.  This  stop- valve  magnet  requires 
from  5  to  8  volts  at  its  terminals  to  operate.  At  signals  C  and 
D,  the  same  connections  obtain.  The  key  switch-box  is  in 
series  with  m,  so  that  when  the  brakeman  turns  the  key,  the 
control  circuit  will  be  opened. 


ELECTRIC  RAILWAY  SYSTEMS 


223 


i 

1 


\ 


\ 


B 


224  AUTOMATIC  BLOCK  SIGNALS 

If  the  switch  at  A  were  closed,  the  visual  signal  would  be 
in  the  clear  position,  hence  m  would  close  its  front  contact. 
This  would  send  a  current  at  a  potential  of  3  volts  through  the 
same  circuit,  but  the  stop-valve  magnet  would  not  operate. 
Its  armature  therefore  remains  in  the  lower  position,  thus 
causing  a  current  to  pass  through  the  safety  recording  magnet, 
H2. 

In  Fig.  199  the  application  to  a  normal  danger  system  is 
shown.  A  train  is  supposed  to  be  in  the  distant  block  of  signal 
A,  the  home  block  being  clear.  The  current  passing  through 
the  home  magnet,  M,  by  way  of  the  armature  of  the  relay,  D, 
raises  m  and  causes  a  current  to  flow  through  the  circuit  shown 
by  the  heavy  lines.  Thus  the  action  of  the  apparatus  is  similar 
to  that  shown  in  the  diagram  for  normal  clear  circuits.  The 
current  through  the  recording  apparatus  is  therefore  the  same 
in  both  cases.  The  latter  is  not  a  required  part  of  the  arrange- 
ment, but  its  use  is  advisable,  since  it  serves  as  a  check  upon 
the  engineman's  statements. 

In  order  that  a  switching  engine  may  make  reverse  move- 
ments at  a  signal,  the  circuit  is  opened  at  the  switch  box, 
which  prevents  the  signal  apparatus  from  operating.  In 
order  to  prevent  failures  in  this  apparatus  from  causing  dis- 
astrous results,  a  detector  circuit  is  employed,  the  relay,  D, 
being  in  this  circuit,  which  is  normally  closed.  A  broken  wire, 
open  or  exhausted  battery,  or  other  defective  condition,  will 
open  the  circuit  at  this  point,  and  throw  the  home  signal  to 
the  danger  position.  This  will  also  cause  the  stop  magnet  to 
operate  if  the  train  passes  the  stop  signal.  If  at  the  same  time 
a  failure  manifests  itself  in  the  locomotive  and  contact-rail 
equipments,  then  disaster  may  accrue.  But  the  probability 
of  such  coincidence  events  occurring  is  remote. 

The  obvious  advantages  of  the  Kinsman  system  are  some- 
what offset  by  the  necessity  of  adding  parts  to  a  car  or  loco- 
motive, in  opening  the  circuit  at  switching  movements,  the 
use  of  contact  rails,  and  the  poor  protection  afforded  to  a  slow- 
moving  freight  train  pushed  by  an  engine  at  its  rear.  An 
automatic  stop,  nevertheless,  removes  one  of  the  greatest  disad- 
vantages of  visual  signaling  devices. 

A  difficulty  encountered  in  a  grounded-return  system  is  the 
disproportionate  current  carried  by  the  track  rails,  which  is 


ELECTRIC  RAILWAY  SYSTEMS  225 

moreover  continually  varying  in  value,  due  to  the  greater  or  less 
conductive  continuity  outside  of  the  rails,  and  the  uncertainty 
of  the  contact  of  the  car  wheels  therewith.  In  one  system 
this  effect  is  overcome  by  making  each  section  a  conducting 
loop  with  heavy  stranded  inductive  bonds  at  the  insulating 
joints,  which  are  electrically  joined  at  their  adjacent  centers. 
A  low-potential  transformer  secondary  with  or  without  an  air- 
gap  in  the  magnetic  circuit  supplies  energy  to  the  section  and 
relays. 

Until  proper  commercial  development  has  occurred  it  would 
be  out  of  place  to  include  a  description  of  such  devices,  how- 
ever meritorious  they  might  appear,  although  several  such  are 
being  considered  by  a  number  of  trunk  lines. 


CHAPTER  XVII. 
MAINTENANCE. 

THE  operation  of  cleaning  the  zinc  and  removing  part  of 
the  more  or  less  saturated  zinc  sulphate  solution  from  a  gravity 
cell  is  known  as  patching.  Owing  to  the  impurities  which 
occur  in  commercial  zinc,  this  element  becomes  coated  to  a 
depth  of  one-half  inch  or  so  with  an  adhesive  brown  or  gray 
mass,  after  about  two  weeks  of  ordinary  continuous  operation. 
This  latter  must  be  removed  at  regular  intervals,  or  it  will 
interfere  with  the  proper  circulation  of  the  liquids,  and  con- 
sequently with  the  operation  of  the  cell.  The  lower  projections 
of  this  deposit  may  either  come  into  direct  contact  with  the 
copper  or  with  the  copper  sulphate  solution,  either  of  which 
will  produce  a  partial  short-circuit  of  the  cell. 

This  mass  is  removed  most  expeditiously  by  a  dull  knife, 
after  which  a  long-handled  brush  with  short  stiff  bristles  is 
used  to  clean  the  zinc  thoroughly.  This  may  be  repeated  until 
but  a  small  amount  of  zinc  remains,  when  a  new  element  must 
be  used.  It  is  never  advisable  to  leave  too  little  or  just  enough 
zinc  for  the  last  run,  as  such  a  proceeding  may  result  in  either 
complete  inoperation  before  the  proper  time,  or,  by  setting  up 
too  weak  a  current,  produce  an  unreliable  movement,  of  the 
track-relay  armature.  Although  failure  of  the  armature  to 
lift  can  only  hold  the  signal  to  which  it  is  connected  at  the 
danger  position,  this  entails  an  unnecessary  loss  of  time  to 
passing  trains. 

Alternating  with  the  operation  of  patching  is  that  of  renew- 
ing. The  liquids  of  the  cell  are  thrown  away,  excepting  about 
one  quart  of  the  zinc  sulphate  solution,  which  is  retained  and 
furnishes  the  initial  sulphuric  acid  for  the  renewed  cell.  The 
zinc  and  copper  are  cleaned  of  their  deposits,  and  the  undissolved 
crystals  of  bluestone  saved.  Two  pounds  of  new  bluestone  are 
added,  and  after  the  quart  of  old  solution  has  been  replaced, 
the  cell  is  filled  to  the  proper  height  with  clean  water.  Renew- 

226 


MAINTENANCE 


227 


ing  is  a  wasteful  process,  but  it  has  not  been  found  practicable 
to  save  the  saturated  copper  sulphate  solution.  The  scraps  of 
copper,  however,  are  returned  to  the  supply  house.  Patching 
and  renewing  are  performed  each  month,  so  that  the  battery- 
man  goes  over  his  territory  every  two  weeks.  This  territory, 
on  a  double-track  road,  may  be  of  from  15  to  30  miles  in  length. 
All  joints  in  the  wiring  of  a  signal  system  must  be  soldered. 
The  best  way  of  accomplishing  this  is  by  means  of  molten 
solder  in  a  crucible  or  pot,  which  is  poured  over  the  cleaned  and 
fluxed  joint  by  a  ladle.  All  traces  of  flux  are  thus  removed, 
and  a  thoroughly  heated  joint  with  a  minimum  amount  of 
superfluous  solder  results.  After  being  soldered,  the  joint  is 


B 


/  /  /  /  /  / 


FIG.  200 

carefully  taped,  preferably  first  with  rubber  strip,  the  latter 
being  covered  with  a  thin  layer  of  binding  tape.  The  finishing 
consists  in  either  gently  heating  the  joint,  or  painting  with  a 
quick  drying  waterproof  solution. 

The  proper  joining  of  copper  conductors  to  the  steel  rail  is 
a  matter  of  primary  importance,  a  certain  amount  of  skill  being 
required.  In  Fig.  200,  A  is  the  formed  iron  wire  end  which  is 
to  be  connected  to  the  rail  by  channel  pins  or  plugs,  for  either 
a  relay,  controller,  or  battery  connection.  At  B  the  wire  is 
twisted,  which  constitutes  the  second  step,  and  C  shows  an 
insulated  copper  wire  inserted  in  the  loop,  the  insulation  being 
removed  from  the  loop  to  the  end.  This  wire  is  twisted  around 
the  iron,  forming  Z),  after  which  it  is  soldered,  as  at  E,  near  the 


228 


AUTOMATIC  BLOCK  SIGNALS 


end  of  the  joint,  so  that  the  insulation  will  remain  uninjured. 
After  making  sure  that  not  a  trace  of  flux  remains,  the  joint  is 
taped  carefully,  as  shown  at  F. 

The  manner  of  connecting  and  housing  such  a  taped  joint  is 
shown  in  Fig.  201.  A  gives  a  section  of  the  rail  and  an  end  view 
of  the  wood  trunking  or  duct;  B  is  a  longitudinal  section,  and  C 
an  elevation.  The  weather  cap,  D,  is  shown  removed  at  B. 

Track  batteries  should  be  frequently  and  carefully  inspected 
to  determine  not  only  their  physical  condition,  but  their  elec- 
trical performance  when  operating.  Faulty  or  dirty  connec- 
tions may  result  in  the  addition  of  considerable  resistance. 


FIG.  201 

Thus,  in  taking  a  millivoltmeter  reading  across  the  cells,  and  at 
the  track,  if  even  a  slight  difference  occurs,  a  high  resistance 
may  occur  between  these  two  points.  This  may  be  due  to 
faulty  connections,  too  much  or  too  fine  wire,  and,  in  some  cases, 
imperfect  contacts  at  the  pole-changing  switch. 

A  relay  which  fails  to  close  its  armature  circuit  with  its  mini- 
mum current  should  be  at  once  replaced,  and  contacts  that 
have  been  fused  by  lightning  and  then  separated  should  be 
discarded.  When  track  sections  are  inspected,  the  bonding, 
insulating  joints,  condition  of  the  ballast,  rail  connections,  and 
line  wires  should  also  be  given  attention.  It  is  well  to  make 
memoranda  of  everything  noted,  so  that  local  operative  con- 
ditions may  be  deduced  from  the  data  thus  obtained.  The 


MAINTENANCE 


229 


numbers  of  all  cut-sections  and  signals  should  be  tabulated, 
thus  systematizing  the  entire  territory. 

When  a  battery  reading  is  obtained  at  one  end  of  a  section, 
it  should  be  compared  with  the  reading  at  the  other  end  of  this 
section.  Either  may  be  the  battery  or  relay  ends,  depending 
upon  the  direction  taken.  Proper  drainage  of  the  roadbed  must 
be  insisted  upon;  and  the  relative  amount  of  moisture  present 
may  be  found  by  these  readings. 

In  hot  weather  the  expansion  of  the  rails  may  force  the 
fiber  rail-ends  slightly  above  the  level  of  the  rail  face.  Passing 
trains  then  pound  off  this  projecting  piece,  ultimately  destroy- 
ing the  fiber,  and  sometimes  causing  the  upset  parts  of  the  rail 
to  come  into  contact.  This  results  in  one  side  of  the  adjacent 


ABC  D  E  F  G  H  I  JKLMNOPQ.  R  S 


1.3 
J.I 

^ 

^ 

*> 

^ 

^ 

-- 

^ 

.9 
.6 
.? 

'  —  • 

h^ 

396O 

' 

• 

\ 

O         600      J20O     J800    ZtOO    3000    3600 
feet 

FIG.  202 

sections  being  connected,  interfering  with  the  normal  operation 
of  the  system  This  is  a  condition  that  is  difficult  to  remedy, 
and  replacing  of  the  rail  end  must  ultimately  be  resorted  to. 

In  Fig.  202  (which  shows  one  square  for  each  one  hundred 
in  the  original),  the  voltmeter  readings  obtained  from  a  typical 
wireless  cut-section  have  been  plotted.  The  cross-section  paper 
on  which  the  results  are  given  should  allow  one  vertical  division 
for  each  one-hundredth  of  a  volt,  or  100  divisions  per  volt. 
Each  horizontal  division  may  be  equivalent  to  one  rail  length,  or 

5280 
30  feet,  there  being — —  =  176  divisions  per  mile  of  track.    The 

voltage  curve  is  found  by  joining  the  points  of  intersection  of 
the  voltage  reading  obtained  at  each  ten-rail  section  with  the 
horizontal  equivalent'  of  the  number  of  rail  lengths  from  the 


230  AUTOMATIC  BLOCK  SIGNALS 

starting  point.  The  voltage  is  measured  at  each  change  in 
connections.  At  A  we  have  the  voltage  at  the  battery  ter- 
minals; B  is  the  voltage  at  the  terminals  of  the  polarity  changer; 
C  at  the  connection  of  the  pole-changing  switch  with  the  track 
wires;  D  the  voltage  between  the  rails;  E  to  Q,  inclusive,  the 
voltage  at  the  various  equidistant  divisions;  Q  that  at  the 
last  rail  length  considered  (No.  132,  or  3960  feet  from  D);  and 
R  and  S  that  at  the  end  of  the  rails  and  terminals  of  the  track 
relay  respectively.  The  reason  for  the  line,  D-Q,  not  being 
straight  is  because  of  the  different  effects  introduced  by  the 
heterogeneous  conditions  of  the  ties,  unequal  depth  of  ballast, 
non-uniform  resistance  of  bond  wires,  and  various  specific  rail 
resistances;  although  this  curve  may  be  taken  as  being  suffi- 
ciently uniform  to  show  good  practice.  The  current  taken 
by  the  relay  (.62  ampere)  was  too  slight  to  introduce  any  per- 
ceptible temperature  effect.  With  a  battery  voltage  of  1.32 
the  following  readings  are  apparent  from  the  curve  at  the 
various  points  where  measurement  was  taken. 

Voltage  at  Volts 

Ay  or  battery  terminals 1 . 32 

B,  or  pole  changer  terminals 1. 32 

C,  or  track  wires 

D,  or  between  rails 


.32 
.28 
.25 
.21 
.18 
.15 
.10 
.06 
.03 


E,  or  between  rails  at      10  rail  lengths ' 

F,  or  between  rails  at      20  rail  lengths 

67,  or  between  rails  at      30  rail  lengths 

jB,  or  between  rails  at      40  rail  lengths 

I,   or  between  rails  at      50  rail  lengths 

t7,   or  between  rails  at      60  rail  lengths 

K,  or  between  rails  at      70  rail  lengths 

L,  or  between  rails  at      80  rail  lengths 1 . 00 

M,  or  between  rails  at      90  rail  lengths 98 

N,  or  between  rails  at    100  rail  lengths 95 

O,  or  between  rails  at    110  rail  lengths 92 

P,  or  between  rails  at     120  rail  lengths 89 

Q,  or  between  rails  at    130  rail  lengths 86 

.R,  or  pole  changer  at     132  rail  lengths 84 

S,  or  track  relay  at    132  rail  lengths 82 

Should  abrupt  changes  occur  in  the  direction  of  such  a  curve, 
it  indicates  that  conditions  at  this  point  are  abnormal.  Thus, 
a  high-resistance  bond  wire,  or  poor  joints  in  a  series  of  rail 


MAINTENANCE  231 

lengths  will  result  in  a  line  which  does  not  conform  to  the 
general  direction  of  the  remainder  of  the  line.  Theoretically, 
the  line  joining  the  points  at  which  indications  are  taken  should 
be  straight,  but  the  factors  above  mentioned  introduce  varia- 
tions of  direction.  Should  considerable  current  leakage  occur, 
the  change  in  the  direction  of  the  line  would  be  at  once  evident. 
The  curve  given  is  a  fair  example  of  what  may  be  expected 
with  gravel  ballast,  with  a  relay  of  3  1-2  ohms  resistance, 
which  requires  a  minimum  of  .23  volts  to  lift  its  armature. 
This  condition  gives  a  wide  possible  variation  of  voltage  through 
which  the  armature  will  rise,  which  is  necessary,  because  of  varia- 
tions in  the  weather  conditions.  On  account  of  the  decrease 
in  the  length  of  air-gap,  and  the  consequent  increase  in  the 
permeability  caused  by  the  motion  of  an  armature,  it  follows 
that  the  minimum  voltages  that  commence  motion  will  produce 
a  good  closing  of  the  contacts. 

The  voltage  of  the  relay  being  .82  and  its  resistance  3.5  ohms, 
the  current  flowing  through  it  will  be  .82  -f-  3.5  or  .234  ampere. 
As  the  output  of  the  battery  is  .62  ampere,  the  relay  evidently 
takes  only  a  fraction  of  the  total  current,  or  38  per  cent;  the 
remainder,  62  per  cent,  being  shunted  across  the  rails  by  the 
ballast  and  timbers,  which  represents  an  average  percentage  of 
leakage,  the  drops  in  potential  in  the  rail  being  also  considered. 

Where  cinders  or  culm  are  intermixed  with  gravel,  or  when 
the  former  are  used  exclusively  as  ballast,  a  material  change 
in  the  readings  obtained  will  be  evident.  This  is  due  to  the 
better  conducting  qualities  of  the  former  and  to  the  better  con- 
tact usually  made  with  the  rail.  Fig.  203  illustrates  an  average 
of  such  cases.  A  battery  of  six  gravity  cells,  connected  in 
multiple,  was  used  in  this  case,  the  current  passing  to  the  rails 
being  one  ampere,  A  being  the  voltage  at  the  battery  and  B  at 
the  track.  From  B  to  M  are  measurements  taken  at  regular 
intervals  of  600  feet  (20  rail  lengths),  the  section  being  7020 
feet  in  length,  N  being  the  track  voltage  at  the  end  of  the 
section,  and  .35  the  voltage  at  the  relay. 

The  relay  resistance  is  3.5  ohms,  with  a  terminal  e.m.f.  of 
.35  volts,  the  current  taken  being  .35  -^  3.5  or  .1  ampere,  the 
remaining  .9  ampere  or  90  per  cent  leakage  through  the  ballast 
from  rail  to  rail. 

This  represents  a  case  where  failure  of  the  relay  to  operate 


232 


AUTOMATIC  BLOCK  SIGNALS 


may  be  expected  in  wet  weather,  owing  to  the  better  conduct- 
ing qualities  of  the  ballast  at  such  times.  Since  .35  volt  is 
just  above  the  operating  e.nuf.  or  such  a  relay,  the  reason  for 
such  failure  is  obvious. 

The  conditions  above  represented  may  be  eliminated  by 
shortening  the  length  of  the  section,  or  by  dividing  it  into  a 
number  of  sections.  If  we  divide  it  into  two  equal  parts,  and 
use  two  sets  of  batteries  and  relays,  the  length  of  each  section 
will  be  3510  feet,  the  e.m.f.  at  the  end  of  the  first  section  will 
be  (from  the  curve)  about  .51  volt,  or  46  per  cent  above 
.35  volt. 

Since  a  greater  relative  gain  is  made  by  excluding  some  of 
the  loss  due  to  the  track  leakage,  the  actual  result  will  be  some- 


.¥ 


J    K   L  M 


1200  2VOO  3600  ¥80O  6000  7200 

feet 

FIG.  203 


what  in  excess  to  the  above.  It  should  be  remembered  that  a 
track  section  must  be  designed  to  give  a  maximum  of  voltage 
at  the  relay,  with  a  minimum  of  leakage,  so  that  a  minimum 
number  of  track  cells  in  multiple  is  required.  Because  of  the 
great  variations  in  the  resistance  and  insulation  of  a  track  sec- 
tion, it  is  not  possible  to  give  a  fixed  rule  as  to  the  voltage 
that  should  be  maintained  at  the  terminals  of  a  relay. 

Numerous  multiple  paths  are  afforded,  even  under  favorable 
conditions,  for  leakage  from  rail  to  rail.  For  this  reason  the 
voltage  across  the  latter  must  be  very  low,  otherwise  the  per- 
centage of  lost  energy  will  be  too  high.  This  voltage,  however, 
could  not  be  excessively  low  (as  for  instance  that  which  would 
be  obtained  from  a  few  thermoelectric  couples  in  series)  or 
relays  could  not  be  satisfactorily  operated,  and  the  shunting 


MAINTENANCE  233 

action  of  a  train  in  a  long  section  might  not  remove  sufficient 
current  from  such  a  relay's  coils.  Ties  are  of  hard  wood  of  high 
specific  resistance,  but  since  from  ten  to  twenty-five  thousand 
spikes  are  driven  in  them  to  the  mile,  it  is  seen  that  the  reduc- 
tion in  insulation  resistance  becomes  very  great  indeed.  Par- 
ticularly is  this  true  when  the  ties  are  wet  and  slate  or  culm 
ballast  is  used.  The  latter  frequently  contains  considerable 
sulphuric  acid,  which,  by  associating  with  the  water,  greatly 
reduces  the  specific  resistance  of  the  ballast. 

With  properly  designed  relays  and  other  current-taking 
devices  a  larger  number  of  cells  should  preferably  be  used  in  the 
main  battery  than  is  required  under  normal  conditions.  This  is 
because  the  cells  ordinarily  used  are  more  efficient  when  a  mod- 
erate current  is  taken  from  them.  Abnormal  current  discharge 
results  in  polarization  (with  concomitant  increase  of  resistance, 
loss,  of  energy,  and  reverse  e.m.f.),  sluggishness  of  chemical 
action,  and  poor  recuperation,  while  the  ampere-hour  capacity 
is  greatly  reduced. 

In  winter,  cells  have  to  withstand  long-continued  low  tem- 
perature, which  decreases  their  terminal  voltage  somewhat,  and 
increases  their  terminal  resistance.  The  drop  in  potential  in  a 
battery  is  thus  much  greater  when  low  temperatures  obtain,  so 
that  the  load  upon  them  is  increased,  especially  when  motors 
are  in  circuit.  Motors  require  heavy  initial  current  discharge, 
so  that  the  voltage  falls  very  rapidly  when  they  are  in  circuit. 
High  voltage  thus  becomes  desirable  in  a  signal  circuit,  and  is 
more  than  compensated  for  in  economy  of  operation.  Another 
argument  for  high  voltage  is  the  liability  of  a  low  potential 
not  overcoming  the  resistance  under  the  motor  brushes 
which  a  particle  of  dirt,  congealed  lubricant,  or  moisture 
interposes. 

To  find  the  insulation  resistance  of  any  circuit,  as,  for  instance, 
that  between  the  rails  of  a  track  section,  having  given  a  volt- 
meter whose  resistance  is  known,  connect  the  latter  in  series 
with  the  resistance  to  be  measured,  and  a  battery  whose  voltage 
is  approximately  equal  to  the  range  of  the  voltmeter  scale. 
After  noting  the  reading,  measure  the  battery  voltage.  Divide 
this  latter  result  by  the  former,  and  add  one  to  the  quotient, 
which,  when  multiplied  by  the  voltmeter  resistance  gives  the 
required  resistance.  Thus  with  a  battery  reading  of  2.8  volts, 


234  AUTOMATIC  BLOCK  SIGNALS 

and  a  resistance  reading  of  .9  volt  with  a  voltmeter  resistance  of 

(28      \ 
— '- — hi)  X  200  =  822 

ohms. 

The  slot  and  slow-releasing  magnets  of  a  normal  clear  two- 
arm  semaphore  signal,  with  a  working  battery  of  16  cells  (11.2 
volts)  require  a  current  of  16  milliamperes  (.016  ampere). 
These  three  magnets,  which  are  connected  in  multiple  with  the 
battery,  have  a  combined  resistance  of  700  ohms,  and  have 
sometimes  equal  resistances,  or  about  2100  ohms  each.  The 
total  current  required  per  day  (assuming  that  the  semaphores 
remain  at  clear)  is,  therefore,  .384  ampere-hour.  The  average 
motor  current  required  is  two  amperes,  the  actual  current  being 
greater  when  the  motor  starts,  and  less  when  full  speed  is  reached, 
due  to  the  full  counter  e.m.f.  which  is  developed  in  the  latter 
case. 

With  100  train  movements  a  day,  both  semaphores  would 
operate  100  times,  so  that  the  motor  actually  operates  200 
times.  With  trains  in  the  block  for  say  three  minutes  each, 
the  slot  magnets  would  not  be  energized  for  300  minutes  out  of 
each  day,  or  5  hours.  The  daily  current  discharge  into  the  slot 
and  slow-releasing  magnets  is  thus  only  .304  ampere-hour.  There 
can  be  eight  blade  movements  per  minute  of  motor  operation, 
so  that  the  motor  will  be  in  use  for  25  minutes  a  day,  or  .416 
hour,  the  current  required  being  .932  ampere-hour,  which, 
added  to  the  .304  ampere-hours  required  for  the  slots,  etc.,  gives 
1.236  ampere-hours.  As  the  capacity  of  the  cells  used  is  ordi- 
narily 300  ampere-hours,  they  will  last  when  operating  this 
signal  for  about  240  days,  allowing  for  some  depreciation. 

When  a  smaller  number  of  train  movements  occur  the  cells 
will  last  longer.  One-arm  signals  could  be  relied  on  to  give  a 
battery  life  of  from  one  to  two  years,  the  latter  being  in  extreme 
cases,  as  the  best  of  cells  cannot  be  left  on  an  intermittent  circuit 
for  so  long  a  time  and  be  depended  upon.  The  resistances  of  the 
compound  slot  magnets  of  a  signal  can  have  high  values,  owing 
to  the  heavy  series  winding  which  carries  the  motor  current  when 
the  latter  is  operating,  and  thus  compensate  for  the  drop  in 
potential  due  to  the  momentary  heavy  demand  on  the  battery. 

Maintainers  and  inspectors  will  find  a  voltmeter  having  two 
scales  desirable:  one  reading  up  to  three  volts,  and  having  fifty 


MAINTENANCE  235 

divisions  per  volt;  and  the  other  reading  up  to  15  volts  with 
ten  divisions  per  volt.  With  the  former  it  is  possible  to  read, 
with  some  show  of  accuracy,  in  millivolts.  A  milliammeter  is 
also  a  useful  prerequisite  to  check  up  the  resistances  and  input 
of  relays  and  other  magnets. 

Motor  brushes  should  be  adjusted  to  exert  only  such  pressure 
upon  the  commutator  as  is  consistant  with  good  electrical 
contact.  The  ends  or  leaves  should  be  spread  apart,  to  avoid 
the  introduction  of  an  open  circuit  by  contact  only  with  one  of 
the  mica  strips  separating  the  bars. 

The  buffers  or  dashpots  on  motor  signals  should  receive 
careful  attention,  otherwise  injury  will  result  to  the  moving 
system  or  too  great  a  retardation  will  occur.  The  vent  should 
be  so  adjusted  that  the  loss  of  speed  (resulting  on  the  tendency 
to  form  a  vacuum)  when  clearing  is  imperceptible.  In  lubri- 
cating, heavy  oil  must  not  be  used  and  care  should  be  taken 
that  dust  or  dirt  does  not  enter  the  buffer  chamber.  A  light 
non-freezing  oil  is  best  for  use  on  all  moving  parts,  including 
the  motor  commutator,  it  being  sparingly  applied  on  the  latter 
by  a  cloth.  When  a  signal  is  in  the  danger  position  all  the 
weight  of  the  moving  system  should  be  borne  by  the  spec- 
tacle casting  and  its  stop.  On  no  account  should  the  slot  be 
impeded  in  any  way. 

The  clearing  of  a  semaphore  by  a  motor  is  a  rather  tedious 
process,  from  six  seconds  to  a  quarter  of  a  minute  being  required. 
With  a  two-arm  arrangement,  the  motor  must  start  up  twice 
when  the  distant  and  home  are  cleared  in  the  proper  sequence 
after  a  train  has  passed  a  signal. 

Relay  boxes  must  be  of  such  construction  that  insects  can- 
not enter,  as  their  operation  sometimes  causes  open  circuits  or 
false  conditions.  They  must  also  be  weatherproof,  although 
extreme  care  need  not  be  exercised,  providing  the  relays  are 
enclosed  in  glass  covers,  which  is  the  present  practice  in  con- 
struction. Motor  armatures  should  also  be  well  protected, 
particularly  at  the  commutator  end,  as  a  trifling  amount  of  dirt 
at  this  part  may  cause  endless  trouble.  Although  an  open 
circuit  in  the  motor  can  only  result  in  a  false  danger  indication, 
this  produces  a  certain  amount  of  delay  to  through  trains. 
All  operated  contacts  must  be  enclosed  in  closed  housings  to 
prevent  access  of  moisture  or  dust. 


FIG,  204 


MAINTENANCE 


237 


Engineers  or  conductors  are  generally  requested  to  fill  out 
blanks  when  held  by  a  signal  for  which  the  immediate  cause 
is  unknown.  These  are  passed  to  the  maintainer  or  inspector, 
whose  duty  is  to  at  once  examine  the  signals  and  accessories 
to  determine  the  cause  of  failure.  Maintainers,  batterymen, 
supervisors,  and  engineers,  with  the  maintenance-of-way  corps, 
exercise  such  a  strict  observance  of  the  working  conditions  that 
it  is  not  often  a  failure  takes  place  undetected.  Such  constant 
supervision,  particularly  on  roads  having  heavy  traffic,  is  abso- 
lutely necessary  to  keep  up  the  integrity  of  a  signal  system. 


FIG.  205 

When  any  serious  trouble  occurs,  its  results  increase  with  great 
rapidity,  owing  to  the  momentous  position  which  signals  possess 
in  a  competent  aggrandization.  Maintainers  must  go  over 
their  entire  territory  immediately  subsequent  to  a  lightning 
storm,  replacing  fuses  and  inspecting  relay  points.  Special 
engines  are  delegated  to  assist  in  performing  this  service,  a 
flurry  of  telegrams  and  messages  being  coincident. 

Continuous  spectacles  and  castings  are  advancing  in  favor, 
and  are  meritorious  because  they  prevent  a  clear  indication 
until  the  semaphore  has  described  more  than  two-thirds  of  its 
working  arc,  also  eliminating  the  complete  shutting  off  of  the 


238 


AUTOMATIC  BLOCK  SIGNALS 


MAINTENANCE 


239 


light  at  any  point  or  angle  of  transition  when  moving  for  an 
indication.    A  drooping  semaphore  may  readily  be  detected  hi 


***»<*•».«  «    ^SpfSS 


daylight  by  the  engineman;  but  in  the  dark  this  is  difficult, 
as  he  is  only  governed  by  the  color  of  the  intercepted  light. 
Hence,  a  partly  cleared  or  improperly  displayed  member,  while 


240  AUTOMATIC  BLOCK  SIGNALS 

readily  perceived  in  the  daytime,  at  night  may  give  a  clear 
indication  when  such  is  wrong.  Sight  shields  only  remedy 
this  difficulty,  by  showing  the  engineman  that  he  must  come  to 
a  stop,  by  reason  of  the  rules  governing  improperly  displayed 
signals. 

Fig.  201  shows  a  generator  and  switchboard  used  in  a  typical 
transmission  scheme  for  storage  battery  charging.-  The  gene- 
rator has  a  terminal  e.m.f.  of  500  volts,  and  in  this  case  is 
bipolar  and  compounded.  The  series  winding  is  shunted  for 
adjustment  of  the  compounding,  an  equalizer  being  used  when 
two  or  more  are  connected  in  multiple.  The  switchboard 
contains,  on  each  side,  a  main  switch,  D,  circuit-breaker  E, 
fuses  F,  ammeter  A  M,  and  a  voltmeter,  V  M,  which  is  thrown 
on  either  side  of  the  lines  by  switch  S.  The  circuit-breaker  will 
open  on  "  no  voltage  "  or  "  reverse  current,"  by  the  action  of 
the  shunt  coil,  A}  or  through  an  overload  by  the  series  coil,  B, 
the  contact  blades  being  shown  at  C.  G  is  a  rheostat  for 
changing  the  terminal  voltage  by  variation  in  the  current  passing 
through  the  shunt  field-coils.  The  individual  storage  batteries, 
both  east  and  west,  are  connected  in  series.  The  use  of  two 
multiple  lines  assures  the  maximum  distance  of  transmission 
at  a  minimum  line  loss. 

We  have,  in  Fig.  205,  a  comprehensive,  normal,  clear  cir- 
cuit, such  as  occurs  on  the  L.  S.  and  M.  S.  R.  R.,  which 
includes  most  of  the  connections  that  have  heretofore  been 
considered.  In  view  of  the  preceding  descriptions,  this  need 
not  be  analyzed,  but  it  covers  the  standard  storage  battery-line 
wire  arrangement  now  being  extensively  applied  to  trunk  lines. 

In  conclusion,  Figs.  206  and  207  contemplate  normal  danger 
circuits  on  the  Erie  Railroad,  from  Bergen,  N.  J.,  to  Suffern, 
N.  Y.  Included  therein  are  slot  control  of  mechanical  sema- 
phores, a  charging  line  arrangement,  and  indicators  at  B  J, 
tower.  This  exemplifies  the  circuits  usually  employed  at  inter- 
locking plants,  and  is  typical  of  the  electrical  control  of  long- 
established  mechanically  operated  semaphores,  and  their  appli- 
cation as  a  supplement  to  an  automatic  network. 


INDEX. 


Advance  signal,  1. 

All-electric  interlocking,  142, 179-200. 

Allentowii  Terminal  B.   R.,  circuits, 

42-47. 

Annunciator,  drop,  168,  159. 
Armature,  use  of  neutral,  61. 

use  of  polarized,  62. 
Arresters,  lightning,  129,  130. 
Atlas  insulated  joint,  101. 
Automatic  motor  brake,  41. 
Automatic  signals  defined,  1. 

Batteries,  84-94. 

types  of,  84. 
Bell  circuits,  38,  40,  42. 
Bell-indicator,  139,  140. 
Block  signals  denned,  1. 
Bonds,  inductive,  225. 

track,  96,  97. 

Brakes,  automatic  motor,  41, 120-122. 
Breakers,  circuit,  25. 

Cells,  renewing  and  patching,  88,  89. 

thermo-electric,  14. 

types  of,  84. 

use  of  primary,  14. 
Charging  storage  batteries,  90-93. 
Circuit  breakers,  25. 

controller,  59. 

controllers,  magnetic,  70-73,  159. 

coupler,  102. 

Circuits,   at  interlocking    tower,   46, 
74. 

crossing  signal,  25. 

controller,  16. 

disk,  15. 

electro-gas  signal,  167-169. 

electro-pneumatic,  160,  161. 

normal  clear,  50-67,  etc. 

normal  danger,  30-49,  etc. 

open  track,  12,  143-146. 

semi-automatic,   18,  48,   49,  68-83, 
etc. 


Circuits—  Continued. 

siding  control,  23. 

simple,  15-29. 

simple  normal  clear,  20. 

simple  normal  danger,  9. 

single  track,  41,  42. 

supplemental  bell,  17,  38-42. 

three-position,  normal  danger,  45-48. 

working,  8. 
Clear  conditions,  false,  10. 

C.  N.  O.  &  T.  R.  R.  circuits,  34-36. 
Coleman's  apparatus,  106-112. 
Common  line,  30-47,  53,  57. 
Commutator,  69. 

Control  circuits,  defined,  8. 
Control,  semi-automatic,  18,  48,  49. 

semi-automatic  track  circuit,  19. 
Controlled  manual  systems,  105-118. 
Controllers,  duplex  rotary,  164,  165. 

rotary  switch  circuit,  163,  164. 

use  of  lever  circuit,  116. 

use  of  duplex  rotary,  117. 

use  of  foot,  118. 
Cut-out,  192,  193. 
Cutouts,  relay,  13. 
Cut-section,  2,  56. 

connections  at,  103,  104. 

Danger  conditions,  false,  10. 
Detector  bars,  use  of,  178. 
Disk  indicator,  132,  138. 

instrument,  132. 

mechanism,  151,  152. 
Distant  signal  control,  16. 

D.  L.  &  W.  R.  R.,  circuits  on,  74-83, 

192,  193. 
Double    electromechanical  slot,   138, 

139. 

route  interlocking,  179. 
semaphore  motor  mechanism,  136- 

138. 
track  circuits,  38,  39,  62,  63. 


241 


242 


INDEX 


Edison  cell,  87. 

Electric  locking,  170-178. 

locking  defined,  170. 

locks,  74. 

railway  signals,  215-225. 

releases,  172,  173. 

slots,  106-110,  113-116,  138,  139. 
Electro-gas  signal  apparatus,  161-167. 

circuits,  167-169. 
Electro-pneumatic  signal  circuits,  160- 

161. 

Erie  R.  R.,  circuits  on,  238-240. 
Eureka  signals,  217-219. 

Failures  at  clear,  11. 
at  danger,  11. 

G.  E.  three-position  circuits,  207  211. 

three-position  signals,  209-214. 
Gordon  cells,  84  86. 
Grafton  three-position  signals  and  cir- 
cuits, 201-207. 

Hall  Signal  Co.  apparatus,  131-141. 

three-position  electro-gas  signal,  214. 
Hewett  open-track  circuits,  143-146. 
Hold-clear  coils,  43. 
Home  signal  defined,  1. 

Indication  of  block's  condition,  2. 
Indicator  circuits,  38. 

disk,  132,  133,  157,  168. 

magnetic  circuit  controller,  70-73. 

polarized,  155,  156. 

semaphore,  157. 

switch,  25,  140. 

use  of  polarized,  13. 
Installing  track  cells  and  relays,  102, 

103. 
Instrument,  disk,  132. 

switch,  140. 

track,  96,  97. 

use  of  switch,  22,  23,  99, 100. 
Insulation  of  switch  rods,  100. 
Interlocking,  all-electric,  42,  179-200. 

machine,  193-196. 

machine  lock,  172. 

relay,  134. 

use  of,  2. 

Joints,  making  wire,  227,  228. 


Key,  spring,  70. 

Kinsman  signals  and   circuits,   221- 
225. 

Lamps,  use  of  incandescent,  43,  44. 
Lehigh  Valley  R.  R.,  circuits,  42^7. 
Leonard's  control  scheme,  112,  113. 
Lever  appurtenances,  195,  196. 

circuit  controller,  68,  72-74. 
Lightning  arresters,  129,  130. 

overcoming  effects  of,  on  relay  con- 
tacts, 126. 

Line-wire  circuits,  22-48. 
Lock  and  block  arrangement,  112. 
Locking,  electric,  171-178. 
L.  S.  &  M.  S.  R.  R.,  circuits  on,  237, 
240. 

Magnetic   circuit    controllers,   70-73, 

175. 

Maintenance,  etc.,  of  signals,  226-240. 
Manual  signal  control,  105,  106. 
Mercury  rectifiers,  use  of,  91-93. 
Missouri  Pacific  R.  R.,  circuits  on,  58, 

60. 
Motor  brakes,  120-122. 

control  relays,  40. 
Motors,  signal,  119-122. 

Neutral  armature,  use  of,  51. 
New  York  subway  signals,  216. 
Normal  clear  circuits,  60-67. 

simple,  20. 

Union,  147-149. 
Normal  danger  circuits,  30-49. 

Hall,  141-146. 

simple,  21-23. 

Outlying  switch  lock  circuits,  175, 176. 
Overlaps,  circuits,  104. 
use  of,  26,  66-64. 

Patching  cells,  226. 
Permissive  signaling,  106. 
Polarized,  armature  use  of,  52. 

normal  clear  circuits,  50-52. 

relay,  123-125,  132. 
Pole  changer,  reversible,  199. 
Preliminary  considerations,  1-14. 
Preparatory  control  functions,  68. 

Quadruple  breaks,  64,  209, 


INDEX 


243 


Rail  joints,  101. 
Rectifiers,  mercury,  91-93. 
Relayed  section,  66,  68. 
Relays,  heavy  current,  125. 

inspection  of,  228-235. 

interlocking,  134. 

motor  control,  40. 

neutral,  126,  134,  136. 

polarized,  123,  125. 

resistance  of,  127. 

slow-releasing,  69. 

Taylor  neutral  track,  123. 

with  glass  housing,  134-135. 

Sector  block,  173,  174. 
Selector,  ground,  199. 

hook,  199,  200. 
Semaphores,  arrangement  of,  3. 

motor  operated,  6. 

principles  of  application,  6,  7. 
Siding  control  circuits,  23,  35,  36. 
Signals,  advance,  1. 

bridge,  6. 

distant,  1. 

external  design  of,  4. 

enclosed  disk,  131, 132. 

electric  railway,  215-225. 

electro-gas,  161-167. 

electro-pneumatic,  160,  161. 

numbering,  2. 

semaphore,  3,  5,  etc. 

semi-automatic,  10,  68. 

three-position,  201-214. 
Slot,  double  electro-mechanical,  138, 
139. 

electric,  106-110. 

magnets,  44,  53. 

slow-releasing,  129. 


Slow-releasing  relay,  68,  152,  153. 
Southern  Pacific  R.  R.,  circuits   on, 
65-59. 

storage  batteries,  89-93. 
Switch  contacts,  use  of,  9. 

indicators,  25,  140,  141. 

instruments,  22,  23,  42,  99, 140. 

lock,  170, 175,  176,  196-198. 

movement,  196-198. 

Tappet  bars,  184. 

Taylor  neutral  track  relay,  123, 

hook  selector,  199-200. 
Telephone  transmitter,  76,  79,  81. 
Three-position    signals    and   circuits, 

45-48,  201-214. 
Track  battery  inspection,  228. 

circuit,  the,  95,  104. 

control,  64. 

instruments,  96,  97. 

simple,  95. 

Tram  staff  control  circuit,  177,  178. 
Transmission  gear,  122,  123. 

TIni  signals,  216,  217. 

Union  Switch  &  Signal  Co.  apparatus, 

147-159. 

normal  clear  circuit,  147-149. 
United  States  signals,  219-221. 

Voltage  curves,  relay,  128,  232. 

battery,  229. 
Voltage,  determining  battery,  228-234. 

Wells,  battery,  93,  94. 

Wireless  or  track  circuits,  141,  143. 

Wires,  bond,  96,  97. 

Working  circuits,  8. 


YC  6V509 


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